Be careful not to confuse the short, small hyphen (-) with the different kinds of the dash (–, ―, —), which are at least twice as long and used for indicating interruptions and additions to a sentence.
• Compound words are composed of two or more words that express one concept together (shown in bold below). They may function as nouns, verbs, or adjectives in the sentence. Compounds come in three forms: open compounds are written with separate words, hyphenated compounds use hyphens, and closed compounds are written as one word.
doing a night shift, the butterfly’s life cycle, suffer from side effects, "She is his partner in crime" (nouns), drop in for a visit, stick up a bank (verbs)
act as a stand-in, call for a time-out, She’s a stick-in-the-mud (nouns), a clear-cut decision, a l ong-term plan, a two-way street, a water-resistant watch (adjectives), to cold-shoulder someone (verbs)
a handbook, be at a standstill (nouns), a longtime friend, a clearheaded woman, a twofold increase (adjectives), to crossbreed species, to handwrite a letter (verbs)
• It is usually difficult to guess what form the compound will take. The solution is to always consult a reliable dictionary, but also take into account that different dictionaries may suggest different forms. This is due to the language constantly changing. Rules regarding compound adjectives will be discussed in our review about the hyphen in punctuation.
• Tip: The older a compound is in use, the more chances to it being written in one word, and vice versa. The hyphenated version tend to be a mid-way stage.
• If one part of the compound is a single letter, it is usually open or hyphenated. The compound email is an exception that has turned into a closed compound, due to pervasive usage.
the H-bomb, y-axis, U-turn
F distribution, V neck, X chromosome
• Do not hyphenate phrases originating form foreign languages, particularly Latin.
a priori, post hoc, vice versa
• The following are commonly hyphenated by mistake, but should be written without hyphens.
more or less, ongoing, under way
• Most prefixes and suffixes are attached to the root word without a hyphen. In some cases, two versions are acceptable ( nonaggressive/non-aggressive, infra-red/infrared), but the tendency nowadays is to omit the hyphen. Only in the cases below should the hyphen be used.
• Use a hyphen after the prefixes all-, ex-, quasi-, and self-. Don’t use a hyphen when self is the root word.
Yes: All-inclusive, ex-husband, self-esteem
No: selfishness, selfless
• Use a hyphen before the suffixes –elect, -odd, and -free.
the president-elect, thirty-odd students, sugar-free
• Use a hyphen when the root word is a numeral.
• Use a hyphen when the root word is capitalized.
pre-Columbian, pre-Reformation, Buddha-like
• Use a hyphen to avoid an awkward looking string of letters.
No: antiintelectual, shellike, multititled, intraarterial
Yes: anti-intellectual, shell-like, multi-titled, intra-arterial
• Use a hyphen if the word would have a different meaning without the hyphen.
The star football player has resigned. (quit)
The star football player has re-signed. (will continue working)
• Use a hyphen if the word would be difficult to read if it weren’t hyphenated.
Coinventor may be read as coin ventor, so write co-inventor
Doubale may be read as doub le, so write do-able
• Use a hyphen when the parts of the compounds are not commonly used together.
Common compounds: worldwide, clockwise
Unusual compounds: community-wide, nutrition-wise
• Use a hyphen with any two-word number (21-99) or fraction.
thirty-two, two hundred fifty-six, one-quarter, 2 and two-thirds
• If the fraction includes a two-word number, hyphenate only that two-word number, as more hyphens may make the fraction unclear
Yes: forty-five hundredths
This has been our review on the hyphen in spelling. For better punctuation, it is no less important that you read our review about the hyphen's roles in punctuation. These include:
• Linking between words of compound adjectives
• Indicating end-of-line word breaks
• Avoiding word repetition