In typewritten material, the hyphen represents an en dash,
and two hyphens with no space around them are preferred for
representing an em dash.
The hyphen 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:
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- hex-
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:
exhunionized 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-inflation
Note: 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 prefer to avoid forming temporary
compounds. Thus, the trend is away from hyphenation.
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 advocate hyphenating unit modifiers only
when necessary to avoid ambiguity. See section unitmodifiers;
the guidelines for hyphenation are repeated here:
-
- A unit modifier should not be hyphenated
- When the unit modifier is a predicate adjective: The
aircraft was flight tested. Note: An
adjective that is hyphenated in the dictionary is
hyphenated as a predicate adjective: The method is well-known.
- When the first element of the unit modifier is a
comparative or superlative: higher order
calculations
- When the first element is an adverb ending in ly:
relatively accurate prediction
- When the unit modifier is a foreign phrase: a priori
condition
- When the unit modifier is a proper name: North
Carolina coast (but Anglo-American plan)
- When the unit modifier has a letter or number
designation as its second element: material 3
properties
- When the unit modifier is enclosed in quotation marks: ``elliptical
style'' symbol list
- When the unit modifier is a scientific name of a
chemical, an animal, or a plant which is not normally
hyphenated: nitric oxide formation
A unit modifier should always be hyphenated
-
- When the unit modifier contains a past or present
participle: flight-tested model, decay-producing
moment
- When the unit modifier is a combination of color terms: blue-gray
residue
- When a connecting word is implied in the unit modifier: lift-drag
ratio, Newton-Raphson iteration
- When the unit modifier contains numbers (other than
number designations): three-degree-of-freedom
simulator, 0.3-metertunnel
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, ``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. 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.
Only rarely would a whole sentence be italicized for
emphasis and never a whole passage. As a matter of fact,
overuse of italics causes them to lose their force. Italics
for special effects ``are used less and less dots, especially
by mature writers who prefer to obtain their effect
structurally dots 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 Style Manual). Consider the
following sentences:
Although holographic interferometry and modulation transfer
function techniques were applied, a simple shadowgraph
system eventually identified the flow-visualization problem.
The flow-visualization problem was eventually identified not
by holographic interferometry, not by modulation transfer
function techniques, but by a simple shadowgraph system.
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
worddifferent).
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
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
Most authorities on style do not indicate whether or not to
italicize report titles; Tichy recommend italics for titles of
long reports. We prefer italic report titles. 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,
G"ottingen), 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 for
more complete information.
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 hDC-3 Space Shuttle ColumbiaF-14 Tomcat Apollo
12Project 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. This rule does not
apply to parentheses and brackets however. Also WIT 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 dashenclose).
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:
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 dots.
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.
When the enumerated list is displayed, a period following
the number is sufficient to set it off (pWIT; and pChic):
The scatterometer is separated into
1.A gimbal 2.A transmitter-receiver assembly 3.Rack-mounted
electronics
Ebbitt 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
(pWIT):
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.
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, but
they are retained for many word abbreviations, particularly
those that may be confused with an unabbreviated word: fig. 1.
269 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
Periods are used in section numbers
1. Introduction 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.)
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.
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 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. 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.
- 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:
- 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.
- Closing quotation marks always follow commas and
periods, regardless of the context.
- Closing quotation marks always precede semicolons and
colons (because they are always dropped at the end of
quoted material).
- Closing quotation marks always follow points of ellipsis
indicating omitted matter in the quote; ending a quote
with ellipsis is rarely necessary.
- Other marks of punctuation (parentheses, question mark)
are placed outside quotation marks if they are not a part
of the quoted matter.
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.
- 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 Alpha = 15.
- 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 dashseparate) or colon (section clauses)
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 hboxevaluations.
- 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.
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 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.
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
-
- Before or after a quotation run in the text
- Before a block quotation beginning with a complete
sentence
- After a block quotation ending with a complete sentence
Points of ellipsis are commonly used with other punctuation
marks. Ellipsis points in a quotation always occur within the
quotation marks. 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.
