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Section 8.9


Use hyphens to link

Also use hyphens for the following purposes:

In typewritten documents, a single hyphen repesents the typographical en dash, adash the width of the letter n. Conventions for using hyphens differ from disciplineto discipline. When in doubt about whether to hyphenate a word, check the appropriate style guide.

To Link Certain Prefixes, Suffixes, Letters, and Numbers withNouns

Use hyphens to connect certain prefixes to nouns. In mostscientific and technical styles, the following prefixes are usually followed by a hyphen:


However, scientific and technical writing styles omit the hyphen between most prefixes, especiallyprefixes that are not words themselves. The following list of prefixes that normally are notfollowed by a hyphen is adapted from Scientific Style and Format by the Council ofBiology Editors:

aero electro meta pre
after exo micro pro
ante extra mid pseudo
anti geo mid re
astro hemo mini semi
auto hyper multi sub
bi hypo non super
bio in over supra
chemo infra photo trans
co inter physio un
counter iso poly
de macro post

When adding a prefix to a noun forms ahomograph (a word with two meanings), use a hyphen for clarity.

multiply multi-ply
recover re-cover
unionize un-ionize

Use hyphens to connect numbers or letters used as prefixes to a noun.

the T-cell


Use a hyphen to connect any prefix to a capitalized noun.

post-Newtonian universe

ex-Soviet scientist

In most cases, do not place a hyphen before a suffix. In most scientific and technical styles,however, the following suffixes are preceded by a hyphen.


To Link Compound Nouns

Use a hyphen to link compound nouns, especially when the lack of a hyphen would change themeaning of the term.


light year

[The first term is a unit of measurement, not of time; the second pair of words, on the otherhand, may indicate a year that is not heavy.]

To Link Compound Modifiers

Use a hyphen to connect compound modifiers to promoteclarity and prevent ambiguity.

laser-alignment process [compound modifier + noun]

laser alignment [modifier + noun]

the two-tube combiner

wire-grid aperture cap [aperture cap for a wire grid]

wire grid-aperture cap [a wire cap for a grid aperture]

wire-grid level adjustment

wire grid-level adjustment

heavy-water cavity [a cavity for heavy water]

heavy water cavity [a water cavity that is heavy]

To Link Spelled-Out Numbers

Use a hyphen to join spelled-out numbers from 21 through 99 and spelled-out fractions.

twenty-one moving parts

the thirty-third experiment

four-fifths of the subjects

To Divide Words

In general, avoid dividing words. However, use hyphens to split words at the end of a line toprevent large spaces between words in justified text and noticeably uneven margins in unjustifiedtext. The following guidelines for dividing words are adapted from the Chicago Manual ofStyle and the NASA Style Guide and the Council of Biology Editors'manual.

To Stand for to or through Between Lettersand Numbers

Use hyphens to stand for through or to, especially in bibliographies and reference lists. (However, when a number, letter,or date is preceded by the word from, use the word to instead of ahyphen.)

pages 25-63

sections 15.2-15.8


from 1901 to 1911

Specialized Uses

Use a hyphen in the following circumstances:

Suspended Hyphens

If all unit modifiers in a series end with the same term, the term does not have to be repeatedeach time; for brevity you may suspend the hyphens and use the modified term only at the end ofthe series.

The first-order, second-order, and third-order equations have all beensolved.

The first-, second-, and third-order equations have all been solved.

2- and 3-phase controllers

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