Caution should be exercised when distinguishing whether a succession of words is being used as a compound or whether they simply appear together. Consider, for example, "We know someone should do it and who that some one ought to be."
For better appearance, it may sometimes be necessary to treat alike words which would have different forms when they appear separately; e.g., bumblebee and queen bee, farmhand and ranch hand. In juxtaposition, these and similar words should be made uniform by being printed as two words. This is only a temporary expedient and does not supersede the list.
Combining forms and prefixes are usually printed solid. For greater readability, the hyphen is sometimes used to avoid doubling a vowel (anti-inflation, naso-orbital); to facilitate a normally capitalized word (mid-April, non-European); to assure distinct pronunciation of each element of a compound or ready comprehension of intended meaning (contra-ion, un-ionized); or to join a combining form or prefix to a hyphenated compound (equi-gram-molar, pro-mother-in-law).
As nouns and adjectives, holdup, calldown, layout, makeup, and similar words should be printed solid. Their er derivatives, (holder-up, caller-down, layer-out, and maker-up) require hyphens. Such compounds as run-in, run-on, and tie-in resist quick comprehension when solid. They are therefore hyphenated.
Words spelled alike but pronounced differently, such as tear-dimmed and tearsheet, wind tunnel and windup, are listed under the same keyword.
Words printed flush in the following list combine with the words which follow to indicate solid or hyphenated compounds. A spacemark (#) appearing before an indented entry indicates a two-word form, but two-word forms appearing in the adjective position usually take a hyphen.
To indicate word function, several abbreviations have been appended. They are: adv., adverb; n., noun; v., verb; u.m., unit modifier; pref., prefix; c.f., combining form; and conj., conjunction.
