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NASA SP-7084 |
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Grammar, Punctuation, and Capitalization |
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A Handbook for Technical Writers and Editors |
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Mary K. McCaskill |
Punctuation is placed in text to make meaning clear and to make reading easier. The various punctuation marks perform four functions: they (1) separate (a period separates sentences), (2) group or enclose (parentheses enclose extraneous information), (3) connect (a hyphen connects a unit modifier), and (4) impart meaning (a question mark may make an otherwise declarative sentence interrogative). The function of a punctuation mark is the basis for the rules governing its use and should be the basis for determining whether or not it is needed. The modern tendency is to punctuate to prevent misreading (open style) rather than to use all punctuation that the grammatical structure will allow (close style). Although the open style results in a more inviting product, it does allow subjectivity, perhaps arbitrariness, in the use of some marks, for example, the comma and hyphen. Consistency in the author's or editor's subjective decisions is vital to a well-punctuated report.
This chapter addresses the marks of punctuation, in alphabetical order, presenting their functions, situations when the marks are required or incorrect, and situations when the marks are appropriate but optional. Because the exclamation point is so rare in technical writing, it is not covered herein. Guidelines for its use parallel those for the question mark (section 3.13).
The functions of the apostrophe are to indicate possession; to form the plurals of abbreviations, characters, and signs; and to indicate omitted characters in contractions.
The rules for forming the possessive case of nouns are presented in section possessive. An apostrophe is never used to form the possessive of a personal pronoun.
• We prefer to follow the GPO and to use the 's to form the plural of symbols, abbreviations, acronyms, designations, signs, numbers, and years:
x's
's
C-130's
PMT's
M.A.'s
4's
+'s
1970's
60's
Note: Chicago Manual of Style and WIT recommend that the apostrophe be used in such plural constructions only when necessary to avoid confusion.
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• An 's is used to form the plural of a word referred to as the word itself, but the apostrophe is not necessary when the word retains its meaning:
There can be no ands, ifs, and buts. (meaning no conditions)There can be no and's, if's, and but's. (meaning the words cannot appear)
• The apostrophe indicates letters left out of contractions, for example, it's (it is), Gov't, and nat'l. Since contractions are rare in formal writing, such use of the apostrophe is also rare.
The nonmathematical function of brackets is to enclose editorial insertions, corrections, and comments in quoted material and in reference citations:
"These instruments [the radiometer and scatterometer] have been used successfully aboard satellites as well as aircraft."Boeing Commercial Airplane Co.: Integrated Application of Active Controls Technology. NASA CR-000000, [1977].
Although some authorities (Chicago Press 1982; Skillin et al. 1974; and Ebbitt and Ebbitt 1982) recommend brackets to enclose material within parentheses, particularly in legal and scholarly works, we have not found the nonmathematical use of parentheses within parentheses to be misleading in Langley reports. Thus, we do not recommend that brackets be used.
The function of the colon is to separate and introduce lists, clauses, and quotations, along with several conventional uses. Authorities disagree on usage of the colon and capitalization after a colon. The following guidelines generally correspond to Words Into Type (Skillin et al. 1974).
A colon has the same separating force as a period. It thus brings a sentence almost to a halt (Bernstein 1981).
• Because of its strong separating function, an introductory colon should generally be used only after a complete sentence. In particular, do not use a colon between a verb or preposition and its direct object:
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Wrong |
The components of the rack-mounted electronics are: power supplies, the gimbal controller, . . . |
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Correct |
The components of the rack-mounted electronics are power supplies, the gimbal controller, . . . |
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Wrong |
The scatterometer is separated into: a gimbal, a transmitter-receiver assembly, and rack-mounted electronics. |
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Correct |
The scatterometer is separated into a gimbal, a transmitter-receiver assembly, and rack-mounted electronics. |
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Nor should a colon be used after such introductory phases as that is, for example, and such as (the colon replaces them):
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Wrong |
Microwave instruments are used for remote sensing of environmental variables such as: sea ice, soil moisture, and surface wind speed. |
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Either |
Microwave instruments are used for remote sensing of environmental variables, such as sea ice, soil moisture, and surface wind speed. |
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Or |
Microwave instruments are used for remote sensing of environmental variables: sea ice, soil moisture, and surface wind speed. |
• When items of a list are numbered, the numbers do not affect the punctuation:
The quantities calculated from microwave instruments are (1) radiometer wind speed, (2) radiometer rain rate, and (3) scatterometer wind vector.
Remember that the colon has strong separating force; do not use it where separation is not grammatically desirable.
When using a colon incorrectly, an author probably wants to emphasize the material that follows. The editor should consider a correction that preserves this emphasis, for example, itemization (see section 2.6) or correct use of the colon.
A colon is an elegant way of introducing a list and at the same time emphasizing the elements of the list (by separating them from the rest of the sentence). Such lists might consist of words, phrases (prepositional, infinitive, or noun), or even clauses.
• Use a colon to introduce a list in apposition to a noun:
The scatterometer is separated into three assemblies: a gimbal, a transmitter-receiver assembly, and rack-mounted electronics.
• Use a colon to introduce a list whose introductory statement contains the words as follows or the following:
The rack-mounted electronics consist of the following: power supplies, the gimbal controller, . . .
• Use a colon to introduce a list that amplifies an introductory sentence:
The purpose of this report is twofold: to evaluate the performance of the instruments and to expand the data base.
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One very effective way to emphasize a list, and at the same time make a long list easy to read, is to number and display the list:
The scatterometer is separated into three assemblies:
- A gimbal
- A transmitter-receiver assembly
- Rack-mounted electronics
• When the introduction to a displayed list is not a complete sentence (the items of the list complete it), no colon is used (Chicago Press 1982; and Skillin et al. 1974):
The purposes of this report are
- To evaluate the performance of the instruments
- To expand the data base
There is a trend toward using a colon after a verb preceding a displayed list (are in the above example). Such use of the colon is grammatically suspect and unnecessary.
A colon may be used between two clauses when the second amplifies or restates the first, for example,
The toughness of pseudo-maraging steel degrades at cryogenic temperatures: at -320 deg F, its Charpy impact energy is 6 ft-lb.Note: The first word after a colon may be capital only when the capital begins a complete sentence; however, capitalization of a complete sentence after a colon is optional.
The dash (section 3.6.2) and semicolon (section 3.15.1) may also be used in this situation. The colon is more formal than the dash and has more introductory force than the semicolon.
A colon is particularly useful for introducing displayed equations (which can be considered clauses), particularly when the equation symbolically restates the preceding sentence:
The out-of-plane deflection wo can be approximated by a truncated kinematically admissable series:
wo w2k-1 cos [(2k -1)
]
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A colon may be used to introduce a direct quotation, particularly if the quote is long (more than one sentence) or not built closely into the sentence (Ebbitt and Ebbitt 1982):
In reference 6, he states this conclusion: "Thermal neutron fluxes up to 1020 might be required."
However, a comma is usually sufficient for direct quotations (section 3.5.1):
In reference 6, he states, "Thermal neutron fluxes up to 1020 might be required."
Neither a colon nor a comma should be used before an indirect quotation:
In reference 6, he concludes that thermal neutron fluxes up to 1020 might be required.
The colon is used by convention as follows:
A colon follows closing parentheses and closing quotation marks.
Of all the marks of punctuation, the comma requires the most judgment. To punctuate with commas requires not only compliance with a set of rules but also thorough understanding of the material being punctuated. Commas can change meaning!
The primary functions of the comma are to separate and to enclose elements of a sentence. The function of a particular comma is important: when it separates, it stands alone, but when it encloses, it needs a partner. The instances when commas separate sentence elements are discussed first in this section, and then the instances when commas enclose.
Many separating uses of the comma are optional in an open style. If commas are used whenever possible, they chop up the text and can even render it difficult to read, contrary to the purpose of punctuation.
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Independent clauses joined by coordinate conjunctions (see section 1.8.1) may be separated by a comma:
The mixing noise dominates the spectrum, but the background noise peaks at a high frequency.
• When the independent clauses are short and closely related, the comma may be omitted:
Each performance of an experiment is called a trial and its result is called an outcome.
The comma is usually retained between clauses joined by the coordinate conjunctions but and for, in order to emphasize the contrast.
• When the independent clauses are complicated and contain internal commas, a semicolon may be used to separate them.
• Do not use a comma to separate independent clauses without a coordinate conjunction:
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Wrong |
The differences were generally about 11 percent, however,
larger differences occurred at |
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Either |
The differences were generally about 11 percent, but
larger differences occurred at |
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Or |
The differences were generally about 11 percent; however,
larger differences occurred at |
• Do not separate compound predicates with a comma unless they are long and require a comma for clarity.
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Poor |
Viewing through the atmosphere increases the apparent reflectance for low-reflectance objects (e.g., p = 0.1), and decreases the apparent reflectance for high-reflectance objects (e.g., p = 0.7). |
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Correct |
Viewing through the atmosphere increases the apparent reflectance for low-reflectance objects (e.g., p = 0.1) and decreases the apparent reflectance for high-reflectance objects (e.g., p = 0.7). |
When compound predicates are so long that a comma seems appropriate, they are perhaps too long. A comma to separate them may not sufficiently clarify them.
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Commas (at least) are required to separate series of three or more elements:
The flight navigation system also provides altitude, roll, pitch, yaw, and ground speed.Pressures at the bulkhead, in the cove, and at the seal were measured.
Wind speed is obtained from antenna brightness temperature, rain rate is obtained from the brightness temperature difference at two frequencies, and wind vector is obtained from radar cross section.
We prefer a comma before the conjunction in a series. This serial comma is often necessary to prevent misreading.
A comma may be used to separate an introductory phrase or clause from the main clause:
If the variable t is actually time, then a is frequency.As discussed in reference 4, one has considerable freedom in defining the Fourier transform pair.
It is standard practice to put the comma after all introductory clauses and all introductory phrases containing a verb form (Ebbitt and Ebbitt 1982):
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Clause |
Although some mathematicians are not comfortable with this intuitive definition, it is widely used. |
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Participal phrase |
Called mean square calculus, this theory is based on the concept of mean square convergence. |
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Gerund phrase |
In analyzing the experiment, we try to statistically describe the whole random process. |
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Infinitive phrase |
To understand this concept, note that periodic functions may be expanded in Fourier series. |
The comma is optional after a short introductory adverbial phrase unless the comma is required for clarity:
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Either |
In recent years, the delta function has been rigorously defined. |
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Or |
In recent years the delta function has been rigorously defined. |
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Wrong |
Soon after the photon density becomes steady as gains and losses balance each other. |
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Better |
Soon after, the photon density becomes steady as gains and losses balance each other. |
• Do not place a comma after an introductory phrase that immediately precedes the verb it modifies:
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Wrong |
Only in recent years, has the delta function been rigorously defined. |
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Correct |
Only in recent years has the delta function been rigorously defined. |
Remember that after introductory clauses and phrases the comma is separating, not enclosing. A comma is appropriate after an internal phrase or clause, but it is not appropriate before unless the phrase or clause is nonrestrictive (see section commasenclose).
• A comma follows, but does not precede, restrictive introductory elements:
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Wrong |
Recombination rate is larger than quenching rate, and, after lasing is achieved, both are smaller than photo-break dissociation rate. |
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Correct |
Recombination rate is larger than quenching rate, and after lasing is achieved, both are smaller than photo-break dissociation rate. |
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Wrong |
The laser pulse was reasonably stationary, although, at 1.6 msec, motion of the arc is evident. |
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Correct |
The laser pulse was reasonably stationary, although at 1.6 msec,motion of the arc is evident. |
• A comma both precedes and follows nonrestrictive introductory elements:
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Correct |
Note that, even though they are unbounded, the delta functions are plotted as arrows with their heights representing the coefficient magnitudes. |
"Adjectives are coordinate if (1) they can be linked by and and (2) they independently modify the substantive" (Linton 1962).
• Separate by commas only those consecutive adjectives that are coordinate. Deciding whether adjectives are coordinate can be tricky; two tests might help. First try inserting and between the adjectives:
The delta function has a long controversial history. (long and controversial?)
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A comma is appropriate between long and controversial.
Consider a linear shift-invariant system. (linear and shift-invariant?)
If still in doubt, try reversing the adjectives (if they independently modify the noun, order makes no difference):
Consider a shift-invariant linear system.
The adjectives shift-invariant and linear are probably coordinate, but the final decision requires someone who understands the technical meaning of the adjectives. (Good luck with trying to explain this grammatical dilemma!)
When in doubt, do not insert the comma between adjectives. The current tendency is to omit the comma between two coordinate adjectives anyway (Ebbitt and Ebbitt 1982). The comma adds emphasis though to the adjectives as separate modifiers.
When clauses in a sentence contain repeated elements (for example, the verb), the omission of these elements is indicated by a comma:
Wind speed is obtained from antenna brightness temperature; rain rate, from the brightness temperature difference at two frequencies; and wind vector, from radar cross section.
The comma may be omitted if the clauses are short:
Wind speed is obtained from antenna brightness temperature, and wind vector from radar cross section.Note: See section 3.15.4 for the use of the semicolon in elliptical constructions.
Direct quotations and questions are separated from the rest of the sentence with either commas or colons. A colon is used to introduce a long or formal quotation.
• Separate a direct quotation or question from the rest of the sentence with a comma:
In reference 6, he states, "Thermal neutron fluxes up to 1020 might be required."The obvious question is, how good is this estimate?
Note: The first word of the question may or may not be capitalized.
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• Neither a comma nor a colon sets off an indirect quotation or one that is part of the grammatical structure of the sentence:
In reference 6, he stated that thermal neutron fluxes up to 1020 may be required.In case of fire, the command for stopping the test is "Recover, fire."
A comma that encloses requires a partner, which may be another comma or a colon, semicolon, period, question mark, or exclamation mark.
A nonrestrictive modifier does not affect the meaning of the basic sentence; it could be removed from the sentence without altering meaning.
• Nonrestrictive modifiers must be enclosed by commas (at least). The important point to remember is that an enclosing comma requires a partner, which can be another comma or another mark of punctuation.
The nonrestrictive prepositional and verbal phrases are enclosed with commas in the following examples:
The record need not be continuous but may, in fact, be digital data.Theoreticians prefer to work in terms of radian frequency, defined for both positive and negative frequencies.
The power spectral density is integrated over some finite bandwidth, such as a one-third octave.
The second integral, being the integral of an odd function over even limits,is zero.
• Be sure to distinguish between restrictive and nonrestrictive internal phrases that introduce clauses (see section introductory):
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Restrictive |
A random process is stationary if for all n, its nth density function is independent of time. |
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Nonrestrictive |
The coefficient could be placed elsewhere because, though preferred, the placement shown is arbitrary. |
• Nonrestrictive relative clauses are enclosed with commas:
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Restrictive |
The most common panel methods are the codes which Hess and Smith (ref. 26) designed for nonlifting bodies. |
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Nonrestrictive |
The most common panel methods are the codes of Hess and Smith (ref. 26), which were developed for nonlifting bodies. |
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• Nonrestrictive adverbial clauses are enclosed with commas:
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Restrictive |
The last chapter introduces specialized areas where research is in progress. |
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Nonrestrictive |
The power spectral density of the signal is shown in figure 9, where arrows represent delta functions. |
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Restrictive |
Two random processes are uncorrelated if their cross correlation satisfies equation (6). |
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Nonrestrictive |
Independent random processes are uncorrelated, since their cross correlation always satisfies equation (6). |
• Whether restrictive or nonrestrictive, an introductory adverbial clause is separated by a comma from the clause it modifies (see section introductory).
• When an internal adverbial clause precedes the clause that it modifies, do not place a comma before it unless it is clearly nonrestrictive:
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Wrong |
Recombination rate is larger than quenching rate, and, after lasing is achieved, both are smaller than photo-break dissociation rate. |
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Correct |
Recombination rate is larger than quenching rate, and after lasing is achieved, both are smaller than photo-break dissociation rate. |
The following guidelines, taken from Rowland, might be helpful in determining whether the clause is restrictive or nonrestrictive. Adverbial clauses can be categorized as follows:
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Words or phrases in apposition are enclosed by commas unless the appositive is restrictive. A restrictive appositive is required to distinguish its antecedent from other members of the same class:
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Restrictive |
The noble gas argon was chosen for the lasant gas. |
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Nonrestrictive |
Argon, the lightest noble gas that will lase, was chosen for the lasant gas. |
• Dashes (em) may enclose appositives to improve clarity, particularly when the appositive contains commas (section dashenclose).
• The word or often precedes nonrestrictive appositives. The appositional or always requires enclosure:
The concept of a laser powered directly by nuclear energy, or a direct nuclear-pumped laser, came into existence shortly after discovery of the laser.
• Commas are usually omitted around symbolic appositives, whether restrictive or not:
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Restrictive |
The coefficients CL and Cm are plotted in figure 23. |
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Nonrestrictive |
The lift coefficient CL is plotted in figure 23. |
However, if the author or editor prefers, nonrestrictive symbolic appositives may be enclosed by commas:
The two most sensitive parameters in the estimations,
and 
are compared with measured values in table II.
Parenthetical phrases, rhetorical adverbs, antithetical phrases, introductory words, and other interruptive sentence elements may be enclosed by commas when they are nonrestrictive:
• Parenthetical phrase
Auxiliary meteorological data used herein, such as vorticity, have been computed from NMC isobaric height fields.
• Rhetorical adverb
The time between independent measurements cannot be reliably estimated; it can be assumed, however, to lie between 20 and 120 minutes.Note: The placement and punctuation of rhetorical adverbs affect emphasis (see section 2.6).
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• Antithetical elements
In winter, clouds near the tropopause are associated with negative vorticity, not with positive vorticity as most meteorologists are accustomed to believing.
• Interruptive words or phrases
For 33-mm-diameter particles, for example, partial loss of laminar flow is predicted for large number densities.
Enclose by commas a phrase with termination that also reads back to a previous phrase:
An aircraft flying through clouds will lose a significant portion, if not all, of its laminar flow.The particle-concentration data have nearly the same latitudinal, but a significantly different seasonal, distribution from that of the cloud-encounter data.
A nominative absolute phrase (that is, a noun with no grammatical function in the sentence modified by a participle) is nonrestrictive and thus is enclosed by commas:
Most confidence may be placed in the statistics for the 30 deg N to 60 deg N latitude band, more data having been taken at these latitudes.
The following conventional uses of the comma should be considered enclosure rather than separation:
• Dates
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The study was conducted from January 15, 1975, to February 1, 1979, aboard commercial airliners. |
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But |
The study was conducted from January 1975 to February 1979 aboard commercial airliners. |
• Geographical names and addresses
These instruments were carried on commercial airliners en route from Chicago, Illinois, to London, England.The computer program is available from COSMIC, 112 Barrow Hall, University of Georgia, Athens, GA 30602.
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• Specifying phrases
This conclusion was drawn from data in Volume II, page 157, of reference 16.
• Degrees, titles, affiliations, etc.
Members of the committee consisted of J. J. Deluisi, Ph.D., NOAA Environmental Research Laboratory; J. P. Friend III, Drexel University; and M. P. McCormick, chairman, NASA Langley Research Center.
• Names
Refer to the report by J. J. Deluisi, Jr., and James P. Friend III:Deluisi, J. J., Jr.; and Friend, James P., III: Listing of Multi-Spectral dots
The comma is used by convention to separate thousands in numbers of five or more digits; but in technical work, we prefer a (thin) space over a comma because in some foreign languages the comma indicates the decimal point:
• Numbers
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Correct |
There were 88,000 data points, 2500 of which had to be discarded. |
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Preferred |
There were 88 000 data points, 2500 of which had to be discarded. |
Commas are used with other marks of punctuation as follows:
• Commas precede closing quotation marks.
• Commas follow a closing parenthesis if the comma would appear without the parenthetical matter.
• Commas rarely precede an open parenthesis, only if the parenthetical matter clearly limits the following word (see section 3.10).
• Other marks of punctuation--semicolon, colon, dash, period--supercede and replace the comma; thus, the "partner" of an enclosing comma may be another mark of punctuation.
Like the comma, the em dash2 is used both to enclose and to separate, and like the comma, an enclosing dash needs a partner. In fact, enclosing dashes
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are replacements for enclosing commas in order to add emphasis. Ebbitt and Ebbitt (1982) suggest a useful philosophy toward using the dash:
If used sparingly, the dash suggests a definite tone, often a note of surprise or an emphasis equivalent to a mild exclamation. If used regularly in place of commas, colons, and semicolons, it loses all its distinctiveness and becomes a sloppy substitute for conventional punctuation. At its best the dash is a lively, emphatic mark.
Dashes may replace commas in enclosing interrupting elements and non-restrictive modifiers and appositives (see section 3.5.2).
• Dashes are appropriate when a comma might be misread, for example, as a serial comma:
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Wrong |
The lasant gas, argon, and He were allowed to mix for 45 minutes. |
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Better |
The lasant gas--argon--and He were allowed to mix for 45 minutes. |
• Dashes are also appropriate when the enclosed element contains internal commas:
Of the lasant gases studied-argon, xenon, krypton, and neon-argon offers the most promise.The most promising lasant gas-argon, which is the lightest gas studied-produced laser output power of 4 W.
• Use dashes when the enclosed element needs emphasis.
• Enclose by dashes a complete sentence that interrupts another:
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Wrong |
The one-sided spectrum, engineers call it simply |
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Correct |
The one-sided spectrum-engineers call it simply "spectrum"-is the output of most spectral analyzers. |
Commas are insufficient to enclose an interrupting sentence; dashes or parentheses are required.
The choice of commas, dashes, or parentheses to enclose a nonrestrictive or interrupting element depends on the relation of the element to the rest of the sentence and on the emphasis it requires ( Effective Revenue Writing 1, IRS 1962):
• Commas (most frequently used) indicate only a slight separation in thought from the rest of the sentence.
• Dashes emphasize the element enclosed and clarify meaning when the element contains internal commas.
• Parentheses indicate that the enclosed element is only loosely connected to the rest of the sentence and therefore tend to de-emphasize it.
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The dash is used to separate sentence elements in essentially three situations:
• A dash separates a group of antecedents from their pronoun that is the subject of the sentence:
Argon, xenon, krypton, and neon--these are the possible choices of noble gases for use in nuclear pumped lasers.
• In a displayed list, a dash may separate the item from an explanatory statement:
Support systems for the facility supply the following:
- Air--The 600-psi system can deliver a flow rate of 300 lb/sec for 3 min.
- Cooling water--The closed-loop system delivers 450 gal/min at 550 psig.
- Gaseous propellants--Hydrogen, oxygen, and nitrogen are supplied from tanks at 2400 psia.
• A dash may separate two clauses when the second amplifies or restates the first:
The toughness of pseudo-maraging steel degrades at cryogenic temperatures--at -320 deg F, its Charpy impact energy is 6 ft-lb.
The colon (section 3.4.1) or semicolon (3.15.1)may also be used for this purpose. The dash is less formal than the colon and more emphatic than the semicolon.
• A dash may precede a phrase like that is, namely, and for example when it introduces a summarizing or explanatory phrase or clause at the end of a sentence, but a comma or semicolon may also be used (Rowland 1962). If an explanatory clause follows the sentence, a semicolon is necessary; if an explanatory phrase follows, a comma is sufficient. If the explanatory phrase or clause receives enough emphasis by being at the end of the sentence, use a comma or semicolon, whichever is appropriate:
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Moderate emphasis |
Other random processes have average properties that vary appreciably with time, for example, the load demand on an electric power generating system. |
|
|
Some random processes are reasonably independent of the precise time; that is, measurements made at different times are similar in their average properties. |
A dash would further emphasize the explanatory material:
|
Emphatic |
Other random processes have average properties that vary appreciably with time--for example, the load demand on an electric power generating system. |
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|
|
Some random processes are reasonably independent of the precise time-that is, measurements made at different times are similar in their average properties. |
The dash is used by convention as follows:
• To separate a title and subtitle
Large Space Systems Technology --1984
Energy Efficient Transport Technology --Program Summary and Bibliography
• In vague or open-ended dates
|
1974-- |
1980 to 19-- |
A semicolon, colon, question mark, period, or exclamation point --but not a comma-- supercede and replace a dash; that is, a semicolon, colon, or period may be the "partner" of an enclosing dash.
The uses of the en dash3 are conventional:
• The en dash indicates inclusive or continuing numbers or dates:
|
pp. 233--235 |
or |
Oct. 1975--Jan. 1976 |
The en dash is not appropriate in a from . . . to . . . or a between . . . and . . . construction:
|
Wrong |
between 1975--1978 |
|
Wrong |
from 1975--1978 |
• The en dash connects a unit modifier with a two-word or hyphenated element:
New York--London flight
shock-wave--boundary-layer interaction
See section 3.16 for discussion of the slash (/) used in place of an en dash.
• The en dash is used in place of a hyphen in all capital text.
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The hyphen4 is used to connect words or parts of words: it connects the syllables of words broken at the ends of lines, it connects prefixes and suffixes to words, and it connects compound words. The modern trend is away from hyphenation. Permanent compounds tend to become solid, and temporary compounds tend to be hyphenated only when necessary to avoid ambiguity.
Words may be hyphenated at the ends of lines between syllables. Proper places to break words are determined from your favorite dictionary. We prefer
Webster's Third New International Dictionary of the English Language, Unabridged. G.& C. Merriam Co., c.1967.
Webster's Ninth New Collegiate Dictionary. Merriam-Webster, Inc., c.1983.
In general, end-of-line hyphens should be avoided when possible. To avoid extremely ragged right margins in unjustified text or to avoid large spaces between words in justified text, words may be hyphenated at the ends of lines. The following guidelines for end-of-line hyphenation are taken from The Chicago Manual of Style (Chicago Press 1982):
• Words may be divided only between syllables. Consult a dictionary for syllabification.
• Divisions leaving one letter at the end or beginning of a line are not permissible.
• Two-letter syllables may be left at the end of a line, but two-letter endings may not be carried to the next line.
• The last word of a paragraph, page, or similar item (e.g., reference citation, figure caption) should not be divided.
• A hyphenated compound should be divided only at the hyphen. Likewise it is best to divide solid compounds at the natural breaks (after-body), after prefixes (dis-comfort), and before suffixes (other-wise).
• Avoid, if possible, several consecutive end-of-line hyphens.
Hyphens are sometimes used to connect a prefix to a word. The tendency is to eliminate the hyphen after a prefix.
• Hyphens are always required with the following prefixes:
|
all- |
quasi- |
|
half- |
self- |
|
quarter- |
ex- |
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• Use a hyphen to attach a prefix to a proper noun or adjective:
un-American
anti-Arab
• Hyphenate a homograph (a word with two meanings) that might be misunderstood without the hyphen:
unionized
un-ionized
recover
re-cover
coop
co-op
multiply
multi-ply
• Hyphenate a word that might be misread or difficult to read without the hyphen:
un-uniform
post-stall
sub-subcommittee
• When a vowel would be doubled or a consonant tripled, use the hyphen:
micro-organism
anti-inflationNote: The prefixes co, de, pre, pro, and re are printed solid even if a vowel will be doubled:
cooperation
preexist
• Use a hyphen to attach a prefix to a hyphenated compound word:
non-civil-service position
pseudo-steady-state system
Hyphens are rarely used to connect a suffix to a word.
• Use the hyphen to avoid tripling a consonant:
shell-like
hull-less
• Use the hyphen when the suffix like is attached to a proper noun.
Compound words may be (1) permanent, their form (solid or hyphenated) being determined by usage and often appearing in dictionaries, or (2)temporary, being hyphenated. Most permanent compounds tend to become solid (without hyphen) with usage, and most authorities (Bernstein 1981; G.P.O. 1984; and Skillin et al. 1974) prefer to avoid forming temporary compounds. Thus, the trend is away from hyphenation.
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Most permanent prepositional-phrase compound nouns are hyphenated, and most other permanent compound nouns are solid:
right-of-way
workbench
mother-in-law
cupboard
Some noun phrases are in the process of becoming permanent compounds; but although they are defined in the dictionary, they are not yet hyphenated. For example, Webster's Ninth New Collegiate Dictionary lists
|
|
right-of-way, n. & adj. |
|
|
But |
|
state of the art, n.; state-of-the-art, adj. |
The dictionary is the best source for hyphenation and spelling of permanent compound nouns.
Formation of a temporary compound noun with a hyphen is appropriate when a combination of several nouns is one entity:
wing-body
writer-editor
Hyphenate an active compound verb derived from a noun form consisting of separate words:
Langley flight-tested that configuration.
To cross-brace such a structure is impossible.
But the passive verb form need not be hyphenated:
That configuration was flight tested.
Such a structure could not be cross braced.
Most authorities (for example, Bernstein 1981 and G.P.O. 1984) advocate hyphenating unit modifiers only when necessary to avoid ambiguity. See section 1.5.2; the guidelines for hyphenation are repeated here:
• A unit modifier should not be hyphenated
Note: An adjective that is hyphenated in the dictionary is hyphenated as a predicate adjective: The method is well-known.
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• A unit modifier should always be hyphenated
Why is a section on italics appearing in a chapter on punctuation? The purpose of italics very closely resembles the purpose of punctuation, to make meaning clear and reading easier. According to Words Into Type (Skillin et al. 1974), "Italics are used to distinguish letters, words, or phrases from the rest of the sentence so that the writer's thought or the meaning and use of the italicized words will be quickly understood." Italics are used to distinguish elements to be emphasized, special terminology, symbols, and words or letters to be differentiated from text. In addition, there are several conventional uses for italics.
In typewritten text, underscore replaces italics and should be used only when absolutely necessary. In many instances, underscore is not used in typewritten text when italics would be appropriate in typeset text.
Words may be italicized when they would be stressed if spoken (Ebbitt and Ebbitt 1982). Italics are especially appropriate if the emphasis would be lost when written:
Of all the events affecting Langley history, only two have caused major trauma. The second was the Sputnik crisis.
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Only rarely would a whole sentence be italicized for emphasis and never a whole passage (Chicago Press 1982). As a matter of fact, overuse of italics causes them to lose their force. Italics for special effects "are used less and less ..., especially by mature writers who prefer to obtain their effect structurally ... writers who find themselves underlining frequently for emphasis might consider (1) whether many of the italics are not superfluous, the emphasis being apparent from the context, or (2) if the emphasis is not apparent, whether it cannot be achieved more gracefully by recasting the sentence" (Chicago Press 1982). Consider the following sentences:
Although holographic interferometry and modulation transfer function techniques were applied, a simple shadowgraph system eventually identified the flow-visualization problem.
A key term in a discussion or a technical term accompanied by its definition is often italicized on first use:
Caustics, concentrations of light corresponding to a family of rays, manifest themselves as bright streaks on the photographs.
For coined terms or technical terms used in a nonstandard way, quotes are preferred to italics (see section 3.14.2).
Italicize a word used not to represent an idea as usual, but as the word itself:
A colon is not used after that is, for example, or such as.
Likewise, letters used as letters are italicized:
The operator presses the letter n to indicate "no" and the letter y to indicate "yes."
Letters indicating shape (V-tail, L-shaped), letter designations (case A, appendix C), and letters indicating subdivisions (figure 1(a), equation (2c)) are not italic. Sans serif letters may be used to indicate shape, but roman type is also acceptable.
Note that the plurals of italic words used as words and italic letters used as letters are formed with roman s's:
and's, if's, and but's
i's and o's
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Most mathematical symbols and letter symbols representing a physical concept are italic, whether within roman or italic text. Chemical symbols, computer symbols, and abbreviations are not italic. Symbols representing vectors, tensors, and matrices may be set in boldface roman type if available.
In typewritten text, we recommend double spacing around symbols to distinguish those that would normally be italic.
There are several items that are italicized by convention:
• Titles and subtitles of books, reports,5 compilations, newspapers, and periodicals are italicized, but not titles of articles, meeting papers, theses, papers in compilations, or patents:
Slater, Philip N. 1980: Remote Sensing---Optics and Optical Systems. Addison-Wesley Publ. Co., Inc.Elterman, L. 1970: Vertical-Attenuation Model With Eight Surface Meteorological Ranges 2 to 14 Kilometers. AFCRL-70-0200, U.S. Air Force, Mar. (Available from DTIC as AD 707 488.)
Bowker, D. E.; Davis, R. E.; Von Ofenheim, W. H. C.; and Myrick, D.~L. 1983: Estimation of Spectral Reflectance Signatures From Spectral Radiance Profiles. Proceedings of the Seventeenth International Symposium on Remote Sensing of Environment, Volume II, Environmental Research Inst. of Michigan, pp. 795--814.
Allen, William A.; and Richardson, Arthur J. 1968: Interaction of Light With a Plant Canopy. J. Opt. Soc. America, vol. 58, no. 8, Aug., pp. 1923--1928.
Weidner, Elizabeth H.; and Drummond, J. Philip 1981: A Parametric Study of Staged Fuel Injector Configurations for Scramjet Applications. AIAA-81-1468, July.
Nemeth, Michael Paul 1983: Buckling Behavior of Orthotropic Composite Plates With Centrally Located Cutouts. Ph.D. Diss., Virginia Polytechnic Inst. & State Univ., May.
• Foreign words that will be unfamiliar to readers are italicized, but not foreign proper names (Challais-Meudon, Gottingen), foreign currency (lira, franc), foreign titles of documents, or foreign phrases that have been adopted into English. (See list of foreign words and phrases, Words Into Type).
• Biological names of genera, species, and varieties are italicized, but not higher classifications. Refer to CBE (1978) for more complete information.
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The name of a specific aircraft, spacecraft, ship, or train is italicized, but not the name or designation of a class of craft or the abbreviations S.S. or H.M.S.:
S.S. United States
but
DC-3
Space Shuttle Columbia
F-14 Tomcat
Apollo 12
Project Apollo
The rules and guidelines discussed so far in this section are based on the assumption that the surrounding text is roman. If the surrounding text is not roman, adjustments must be made:
• The typeface used for symbols remains italic even when the surrounding typeface changes.
• Items other than symbols that are normally set in italic on roman type are set in roman on italic type.
• Items other than symbols that are normally set in italic on roman type may be quoted in caps and small caps or boldface type.
The standard printer's rule is to set punctuation marks in the typeface of the letter preceding them (Chicago Press 1982). This rule does not apply to parentheses and brackets however. Also Skillin et al. (1974) prefer that quotation marks, question marks, and exclamation marks, as well as parentheses, be set according to the context of the sentence.
Parentheses may be used to enclose nonrestrictive or interrupting elements. Commas or dashes may also be used for this purpose (see section 3.6.1).
• Parentheses are most appropriate to enclose a nonrestrictive element that is only loosely connected to the sentence and could be left out without damaging the sentence.
• Do not insert a parenthetical element with no relation whatever to the rest of the sentence. The following example is taken from Fowler (1944):
In writing this straightforward and workmanlike biography of his grandfather (the book was finished before the war and delayed in publication) Mr. Walter Jerrold has aimed at doing justice to Douglas Jerrold ....
The parenthetical idea has no bearing on the sentence!
• Parentheses enclose numbers in an enumeration within a sentence:
The scatterometer is separated into (1) a gimbal, (2) a transmitter-receiver assembly, and (3) rack-mounted electronics.
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When the enumerated list is displayed, a period following the number is sufficient to set it off (Skillin et al. 1974; and Chicago Press 1982):
The scatterometer is separated into
- A gimbal
- A transmitter-receiver assembly
- Rack-mounted electronics
Ebbitt and Ebbitt (1982) neatly explain use of parentheses with other punctuation marks as follows:
When a complete sentence in parentheses comes within a sentence (notice the punctuation of this one), it needs neither a capital letter nor a period. Commas and other marks of punctuation in the main sentence always follow the parenthesis (as here and in the preceding sentence). (A sentence in parentheses, like this one, that does not stand within another sentence has the end punctuation before the closing parenthesis.)
Punctuation (for example, question marks, quotation marks) of the ideas within parentheses remains within parentheses, while punctuation of the main sentence remains outside, almost always after the closing parenthesis rather than before an opening parenthesis. A comma precedes an open parenthesis if the parenthetical matter clearly limits the word following it (Skillin et al. 1974):
Despite these differences, (digital) image-gathering systems can be compared with optical imaging systems.
The period is a mark of separation. Its primary purpose is to separate complete thoughts, to mark the end of declarative and imperative sentences. (Interrogative sentences end with a question mark; exclamatory, with an exclamation point.) The key word here is complete; a period should be used only after a sentence complete with subject and predicate.
• Do not use a period after headings on separate lines (run-in headings are often separated from text by a period), after running heads, after table titles, or after items in an enumerated, displayed list unless one or more of the items are complete sentences:
The purposes of this report are
- To evaluate the performance of instruments
- To expand the data base
We can define the requirements of the power converter as follows:
- .Energy conversion should be high.
- Efficiency should be independent of laser wavelength.
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• It is customary to end figure captions with a period whether or not they are complete sentences:
Figure 1. Computing scheme for algorithm.Figure 1. Concluded.
A period may follow abbreviations except those for units of measure. The trend is away from periods for abbreviations (Skillin et al. 1974; and Chicago Press 1982), but they are retained for many word abbreviations, particularly those that may be confused with an unabbreviated word:
fig. 1
no. 209
Co.
Mr.
• Periods are not used for abbreviations of units of measure (except inch), for acronyms, or for contractions (with apostrophe):
ft
cm
lb
NASA
V/STOL
nat'l
A period does follow the abbreviation for inch
1 in.
but
in/hr
14 lb/in.
in-lb, 6-in-wide
Whether or not to end an abbreviation with a period is best determined by consulting
G.P.O. Style Manual
Webster's Collegiate or Unabridged Dictionary
The period is so useful for separation that several conventional uses exist:
• A period precedes decimal numbers:
0.2
.68
29.32
• A period separates dollars and cents:
$6.50
but
50 cents
• In enumerations, a period usually follows the number or other designator:
Volume I. Theory
Figure 2. Response times.The options are
- Optical rectification
- Laser-driven magnetohydrodynamics
- Laser photovoltaics
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• Periods are used in section numbers
This subject is discussed in section I.A.1 of reference 3 and in section 5.2 of this paper.
A period may be used only with quotation marks, parentheses and brackets, and points of ellipsis, but not with other marks unless the period marks an abbreviation:
(In this fig., the dots denote dots)
(e.g., decimal numbers)
(Why include the following three pp.?)
But a period is never repeated after an abbreviation:
I prefer the abbreviation Ms.
• Place periods before closing quotation marks.
The operator presses the letter n to indicate "no" and the letter y to indicate "yes."The word pultruded is defined to mean the opposite of "extruded."
• Generally periods are placed outside closing parentheses; place the period inside only when a complete parenthetical sentence does not stand within another sentence (see section parens):
(Parenthesized sentences, like this one, that do not stand within other sentences have a period before the closing parenthesis.)
Points of ellipsis (three evenly spaced periods) are used in formal writing to indicate an omission from quoted matter:
This combination caused Wright to wonder whether "since the interference velocities due to . . . walls are of opposite signs . . ., opposite effects might be so combined in a slotted tunnel as to produce zero blockage."
• Ellipsis points should not be used (Chicago Press 1982)
Points of ellipsis are commonly used with other punctuation marks. Ellipsis points in a quotation always occur within the quotation marks.
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Punctuation in the quote before or after the ellipsis should be retained if it will enhance meaning:
"The gangs were of all races and conditions: . . . part of the huge compost of America.""In the city of Hampton alone, hundreds of families emigrated . . ., scores were made jobless, houses were empty and business generally suffered."
• The terminal period (at the end of a sentence) is always retained before an ellipsis and may be retained after ellipsis to enhance meaning:
|
Period before ellipsis |
|
At a Mach number of 0.98, ``the needle of the Mach meter took an abrupt jump past M = 1.0 and went against the peg, which is a distance equal to about 0.05 in Mach number past 1.0. . ..'' |
|
Period after ellipsis |
|
``When the Mach number went off the scale, the pilot shut down all cylinders . . .. Preliminary NASA data work-up indicates that a Mach number of 1.06 was reached.'' |
Note the difference in spacing of periods before and after points of ellipsis.
The purpose of the question mark is to terminate a direct question, whether the question is an independent sentence, a clause within a sentence, or a direct quotation:
What system identification procedure should be used for a statically unstable aircraft?The question addressed by this research project is, What system identification procedure should be used for a statically unstable aircraft?
In reference 2, Jones asks, "What system identification procedure should be used for a statically unstable aircraft?"
When the direct question occurs within a sentence (as in the second example above), the author may or may not choose to capitalize the first word of the question.
• When the question is a single word, such as when, how, or why, within a sentence, neither a question mark nor a capital is necessary; the word is often italicized:
The announcement should answer the questions who, what, where, when, and why.
• A question mark should not follow an indirect question:
This research project addresses what system identification procedure should be used for statically unstable aircraft.
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A question mark may be used with other marks of punctuation as follows:
• The question mark supersedes a period or comma.
• A question mark precedes a closing quotation mark or parenthesis only if it is part of the quoted or parenthetical matter:
Because of the ambiguous use of the slash, the reader might well ask the question, What is meant by "molecular/atomic collision"?The obvious question is, how accurate is this estimate (compared with the accuracy of the input measurements)?
• When the question mark ends a sentence, the period is, of course, omitted. When the question mark does not end the sentence, it should never be followed by a comma; if required, a semicolon may follow a question mark:
The obvious question is, how good is this estimate? and equation (6) provides a tool for answering it.The reader might well ask the question, What is meant by "molecular/atomic collision"?; the slash gives no clue to the meaning.
Quotation marks are used to enclose words quoted from another source, direct discourse, or words requiring differentiation from the surrounding text. Since they enclose, they always come in pairs. They can also be overused and render a text visually hard to read.
Double quotation marks (" ") are used most of the time. Single quotation marks (' ') are used only within double quotation marks.
If a document quotes extensively from other sources, consult an authority, such as Chicago Press (1982), chapter 10, for details of correctly setting up quotations.
Quotation marks enclose material taken verbatim from another source. The quote can be of any length, from a phrase to several paragraphs:
Diehl argued that a transonic research plane was necessary to demonstrate that the sound barrier was "just a steep hill."As Richard P. Hallion has explained: "They gave the fuselage a pointed nose then gradually thickened the body--that is, increased the cross-sectional area--until the fuselage reached its maximum diameter near the middle."
• The source of a quote should always be clear, either from the context or with a reference citation.
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• Long quotations are usually set off from the text and set in smaller type if typeset. Such block quotations are not enclosed by quotation marks:
Stack allowed Whitcomb to present his area rule at the next meeting of Langley's elite technical seminar.At the end of presentation there was silence. Finally, Adolf Busemann stood up. Turning to his colleagues, the pioneer of sweptwing technology remarked, "Some people come up with half-baked ideas and call them theories. Whitcomb comes up with a brilliant idea and calls it a rule of thumb."
Note the double quotes within the quotation. If the quotation had not been set off but had been run in the text and enclosed in quotation marks, then single quotes would have enclosed Busemann's remark.
Quotation marks may enclose words that need to be differentiated from the text in order to make meaning clear. Italics are used for much the same purpose (see section 3.9.3) and are sometimes interchangeable with quotation marks.
• Enclose in quotes a word or phrase whose meaning is being referred to:
The operator presses the letter nto indicate "no" and the letter y to indicate "yes."The word pultruded is defined to mean the opposite of "extruded."
Words used simply as words are usually italicized:
A colon is not used after that is, for example, or such as.
• Enclose words or phrases following entitled, the term, marked, designated, classified, named, enclosed, cited as, referred to as, or signed, but do not enclose an expression following known as, called, or so-called unless the expression is slang (G.P.O. 1984). Of course, an italicized phrase or word (for example, a title) would not be further differentiated with quotation marks.
• Do not routinely enclose slang or technical jargon (if used) in quotation marks, unless it is expected to be foreign to the vocabulary of the reader:
|
Quotes unnec. |
The pilot "captured" the glide slope at an altitude of 300 m. |
|
Quotes OK |
Recently, "cepstrum" analysis has come into prominence; the name is derived from inverting the first four letters in spectrum. |
Such terms are normally quoted only the first time they are used.
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• Enclose in quotation marks coined terms or technical terms used in a nonstandard way:
Synoptic data (or "snapshots" of global parameters) are required.If the results satisfied a set of general, and sometimes intuitive, criteria, they were accepted as being "good."
Such terms are normally quoted only the first time they are used.
• Enclose in quotation marks the titles of parts (sections, chapters) of a report or book and the titles of published papers, articles, etc., that are not italicized (see section 3.9.5):
The aircraft is described in more detail under the section entitled "Flight Facility."The runway is marked in accord with FAA circular AC 150/5300-2B, "Airport Design Standards---Site Requirements for Terminal Navigational Facilities."
Langley drops quotation marks in reference lists and bibliographies; the number of quotes in these sections makes them unsightly and hard to read.
Quotation marks may be used with all other marks of punctuation.
The semicolon separates coordinate clauses, long internally punctuated elements of series, explanatory phrases and clauses, and elliptical clauses. The semicolon denotes nearly a full stop; thus, its uses are as much a matter of personal choice as of correct punctuation.
Coordinate clauses may be joined by a semicolon.
• If coordinate clauses are not joined by a coordinate conjunction, they must be joined by a semicolon:
The first two flight runs for each pilot were treated as practice; only the last four runs were used in the analysis.
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• If coordinate clauses are joined by a coordinate conjunction but the clauses are long, complicated, or internally punctuated with commas, they may be separated by a semicolon:
The pilots unanimously preferred the new display format because of the steadiness of the horizon, runway image, and pitch grid during turbulence; and they felt that this steadiness resulted in less distraction and better situational awareness.
• If coordinate clauses are joined by a conjunctive adverb ( however, thus, therefore, hence), a semicolon (or a period) must precede the conjunctive adverb:
The differences were generally about 11 percent; however, larger differences occurred at
Whether a period, semicolon, or comma is used between clauses is a matter of style. In Writer's Guide and Index to English, Ebbitt and Ebitt discuss semicolons and style: "Semicolons are usually more suitable in the longer, more complicated sentences of formal styles dots. In general styles commas are often used where semicolons might appear in formal writing, or else clauses that could be linked by semicolons are written as separate sentences." A semicolon slows the pace and has more separating force than a comma while still tending to join clauses; a period simply separates sentences. The semicolon is particularly effective between contrasting clauses:
One pilot performed slightly better with the attitude-aligned display; the other pilot performed much worse.
A dash (section 3.6.2) or colon (section 3.4.1) may also separate two clauses when the second amplifies or restates the first. The colon is more formal and has more introductory force than the semicolon, and the dash is more emphatic than the semicolon.
When elements of a series are long, complex, or internally punctuated with commas, separating the elements with commas may not make meaning clear.
• Semicolons may separate elements of a series that are complex or require internal commas:
Committee members were H. Melfi, NASA Goddard Space Flight Center, Greenbelt, Maryland; A. L. Carswell, York University, North York, Canada; and E. V. Browell, NASA Langley Research Center, Hampton, Virginia.
Remember that a semicolon signals nearly a full stop. Semicolons may clarify the elements of a series, but at the same time disrupt the flow:
The goal was to accelerate application of composites to primary structures in new civil transport aircraft by development of design techniques for empennage, wing, and fuselage structures; dissemination of technology throughout the transport industry; and extensive flight service evaluations.
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Another way to clarify the series might be devised, for example, enumeration or rearrangement of elements of the series:
The goal was to accelerate application of composites to primary structures in new civil transport aircraft by (1) development of design techniques for empennage, wing, and fuselage structures, (2) dissemination of technology throughout the transport industry, and (3) extensive flight service evaluations.The goal was to accelerate application of composites to primary structures in new civil transport aircraft by dissemination of technology throughout the transport industry, extensive flight service evaluations, and development of design techniques for empennage, wing, and fuselage structures.
In technical writing explanatory information often follows such introductory phrases as that is, namely, for example, in other words, for instance.
• A semicolon must precede a phrase like that is, namely, and for example when it introduces an independent clause:
Some random processes are reasonably independent of the precise time; that is, measurements made at different times are similar in their average properties.
When commas are necessary to indicate the omission in an elliptical construction, a semicolon separates the elliptical clauses:
Wind speed is obtained from antenna brightness temperature; rain rate, from the brightness temperature difference at two frequencies; and wind vector, from radar cross section.
Of course, if the commas are unnecessary to indicate omission, the semicolon can be replaced by a comma so long as the clauses are joined by a conjunction:
|
Wind speed is obtained from antenna brightness temperature, and wind vector from radar cross section. |
|
|
But |
Wind speed is obtained from antenna brightness temperature; wind vector, from radar cross section. |
Semicolons always follow closing parentheses and quotation marks; semicolons are always dropped at the end of quoted material (Chicago Press 1982).
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A slash, also called solidus or virgule, can be correctly used (1) in and/or, (2) in fractions (x/y), (3) to indicate per (m/sec), and (4) when quoting poetry.
Although most usage and grammar authorities do not acknowledge use of the slash in a temporary compound, it is being widely used to indicate temporary compounds. In drafts of NASA reports, we frequently find such constructions as
hoop/column antenna
boundary-layer/shock-wave interaction
matrices/vectors
lateral/directional characteristics
In the first example (hoop/column), those coining the new technical term seem to have chosen (erroneously) to use a slash rather than a hyphen; however, this term, meaning a combination of a hoop and a column, has been widely used with the slash. In the second example ( boundary-layer/shock-wave interaction), the slash is being used as an en dash, or ``long hyphen.'' In the third example (matrices/vectors), the slash indicates alternatives, a usage that Tichy and Fourdrinier (1988) accept with caution. In the last example (lateral/directional), the slash is being used in a unit modifier that has been hyphenated for years.
These four examples illustrate our objection to use of the slash in temporary compounds: Its meaning is not clear.
• We therefore prefer that the slash be changed to a hyphen,
The 15-m hoop-column antenna is a deployable and restowable structure.
to an en dash,
These phenomena result from shock-wave--boundary-layer interaction.
or to and, or, or and/or,
Operator splitting is additive decomposition of some matrices and vectors in the model.
Of course, some technical terms have become standard with the slash (for example, V/STOL, stall/spin).
• A term that is accepted as standard with a slash may be used with the slash.
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