A hyphen (-) links words that belong together, such as well-known or twenty-one, and joins some prefixes and suffixes to a word, such as ex-boyfriend or ball-like. It is always written without spaces. This article explains the rules and their exceptions.
The hyphen is one of the most frequently used punctuation marks in English. On a keyboard it shares a key with the minus sign, but it has rules of its own. Do not confuse it with the longer dashes, the en dash and the em dash, which are explained in all you need to know about the en dash and em dash.
Rules for using the hyphen
Hyphens are used in two main contexts, and this article follows them:
- between words;
- with prefixes and suffixes.
Hyphens between words
The main purpose of the hyphen is to link two or more words, to show that they belong together in meaning. Some compounds are always hyphenated. You can look them up in any dictionary, which lists them in their hyphenated form.
These compounds can be formed from different types of words:
- compound adjectives: It was a live, on-air interview.
- compound verbs: Always double-check your figures.
- compound nouns: She is your typical do-gooder.
Hyphens are common in new compounds that could otherwise confuse readers, and in ages that describe a noun. Numbers from twenty-one to ninety-nine are hyphenated when you write them out in words, which makes them easier to read. Fractions written in words are usually hyphenated as well, but not when a or an takes the place of one: a third, a quarter.
- People who refuse vaccines are often called anti-vaxxers.
- He was a five-year-old boy. (But: He was five years old.)
- Thirty-four, fifty-nine
- Less than two-thirds of the pupils knew the difference between your and you're.
Double-barreled surnames are usually written with a hyphen as well:
- Ms. Claire Butch-Gardener is on the phone.
A hyphen is most useful in a compound adjective that comes before a noun, because it makes your meaning clear. A small-business owner owns a small business, while a small business owner could be a business owner who is small. After the noun, the same words usually need no hyphen: a well-known author, but an author who is well known.
There are also cases where you should not use a hyphen between words. Do not use one after very or after an adverb that ends in -ly: a very good idea, a highly skilled worker. Proper nouns of more than one word are not hyphenated either, even when they describe another noun: a New York restaurant, a Supreme Court decision.
Prefixes and suffixes
Prefixes and suffixes are a very productive part of English. Both are affixes: groups of one or more letters added to the beginning of a word (a prefix) or to its end (a suffix). Other languages have even more kinds of affixes, such as the infix (inserted into a word) or the circumfix (placed around a word).
Prefixes change the meaning of a word, sometimes drastically, while suffixes often change the word class, for example from a noun to an adjective.
Prefixes are hyphenated in some cases, but not always. When you turn safe into unsafe, no hyphen is needed. In the following cases, however, you should use one:
- before a proper noun or a number: mid-August, un-American, pre-2000;
- in family relations with great-: great-great-granddaughter;
- when the prefix ends with the same vowel that the word starts with: anti-inflammatory, semi-industrial;
- with the prefixes self-, ex-, and all-: self-destructive, ex-boyfriend, all-seeing;
- when the word without the hyphen would mean something else: re-cover (cover again) and recover (get better), re-sign (sign again) and resign (quit).
Suffixes are hyphenated far less often than prefixes. Words like applicable or extremism need no hyphen. Use one between a word and its suffix only in a few cases, for example:
- after a proper noun: Picasso-like;
- when the suffix -like would put three l's in a row: ball-like, shell-like;
- with the suffix -elect: president-elect, governor-elect.
When it comes to affixes, it is a good idea to check a dictionary. Most prefixes and suffixes do not need a hyphen. When you form an unusual word with a prefix or a suffix, though, a hyphen can prevent confusion for your readers. The article on in- and un- has more on how prefixes work.
One last rule
One last rule applies to every hyphen, between words and with prefixes and suffixes: do not put a space before or after a hyphen.
The hyphen always sits directly between the letters of the words it joins. The one exception is a hyphen that stands for a word you leave out to avoid repeating it, as in short- and long-term goals. To learn how hyphens and dashes differ, read dashes and hyphens: they're different.