Published on 19 January 2016 by Jack Caulfield. Revised on 20 October 2023.
A hyphen (-) is a punctuation mark used to connect two or more words (or parts of words) to show that they form one unit of sense – e.g., “fast-paced”, “shake-up”, “four-year-old”, “post-punk”.
Mistakes with hyphens are very common: leaving them out when they’re needed, adding them when they’re unnecessary, or putting them in the wrong place. This is mainly because the same series of words may be hyphenated or not depending on the role it plays in a sentence.
This table covers the main guidelines for using hyphens correctly, which are then explained in more detail below.
| Hyphenate … | Don’t hyphenate … |
|---|---|
| Compound adjectives that come before the noun: “well-known rules” | Compound adjectives that appear after the noun: “The rules are well known.” |
| Phrasal verbs used as nouns: “There’s been a break-in!” | Phrasal verbs used as verbs: “The burglar broke in through the skylight.” |
| Some compound nouns, especially if more than two words (check a dictionary): “brother-in-law”, “jack-of-all-trades” | Most compound nouns: “primary school”, “business owner”, “apple pie” |
| Prefixes connected with a numeral or capitalised word, or to avoid confusion with another word: “pre-Columbian”, “mid-1960s”, “re-pair” (meaning “pair again”) | Other prefixes generally: “predate”, “midcentury”, “repair” |
The majority of compound nouns are written as open compounds with spaces between the words (e.g., “primary school”, “house party”, “student nurse”).
Some well-established compound nouns are always written as closed compounds (e.g., “shipbuilding”, “schoolteacher”). And some, especially those consisting of a phrase of three or more words, are always hyphenated (e.g., “mother-in-law”).
Check out the examples below, and check a dictionary if you’re unsure how to write a specific term. If you can’t find a compound noun in the dictionary, write it with spaces by default.
| Open compounds | Hyphenated compounds | Closed compounds |
|---|---|---|
| artificial intelligence, attorney general, common sense, French fries, primary school, house party, living room, roller coaster, search engine, theme park, walking stick | jack-of-all-trades, know-it-all, man-of-war, merry-go-round, runner-up, sister-in-law, stick-in-the-mud, well-being | backpack, boyfriend, breakfast, bypass, checkout, cheesecake, highway, newborn, payout, peanut, smartphone, weekend, wherewithal |
More rarely, a suspended hyphen appears at the start of a word to indicate the repetition of the first word or of a prefix. Style guides often recommend against this usage, as it can be confusing. It’s usually better to just write out both words in full:
When reporting speech—as in a work of fiction or a quote from an interview – hyphens can be used to indicate that the speaker stuttered (repeated a particular part of a word) or that they extended a certain sound.
Examples: Hyphens used to indicate stuttering “I th-th-think we should go b-back inside,” said Charlie, shivering in the cold.
“This is so-o-o bo-o-oring!”
When you spell out a number instead of using a numeral, hyphenation may be required. Style guides usually recommend hyphenating numbers twenty-one to ninety-nine that consist of two words, but not hyphenating hundreds, thousands, and so on.
Examples are shown below for both cardinal (e.g., “twenty-one”) and ordinal numbers (e.g., “twenty-first”).
| Numerals | Cardinal | Ordinal |
|---|---|---|
| 0–20 | zero, one, seven, ten, eleven, nineteen, twenty | zeroth, first, seventh, tenth, eleventh, nineteenth, twentieth |
| 21–99 | twenty-one, forty, fifty-six, seventy-five, ninety-nine | twenty-first, fortieth, fifty-sixth, seventy-fifth, ninety-ninth |
| 100+ | one hundred (and) twenty-five, seven hundred thousand five hundred (and) forty-eight, nineteen thirty-nine (year) | one hundred (and) twenty-fifth, one million seven hundred thousand five hundred (and) forty-eighth |
Note Many style guides recommend writing numbers 10 and above as numerals (e.g., “21st”, “1,700,548”, “1939”), in which case the issue of hyphenation is irrelevant.
There is some disagreement about how to spell out fractions. Traditionally, they are always hyphenated (e.g., “one-third”) unless the second number already contains a hyphen (e.g., “one twenty-fifth”). This approach is still recommended by Chicago and MLA.
A newer approach is to hyphenate fractions only when they are used as adjectives before a noun and leave them open in other contexts. This is recommended by APA and Oxford style guides. Examples of the two approaches are shown in the table below.
| Always hyphenate (Chicago and MLA) | Hyphenate only adjectival fractions (APA and Oxford) |
|---|---|
| The motion passed with a majority of two-thirds. | The motion passed with a majority of two thirds. |
| I’m almost five-eighths of the way through. | I’m almost five eighths of the way through. |
| There’s been a one-half increase in the price of bread. | There’s been a one-half increase in the price of bread. |
| The turkey is three-quarters cooked. | The turkey is three-quarters cooked. |
| You can’t win with a one twenty-fifth share of the vote. | You can’t win with a one twenty-fifth share of the vote. |
If you use a non-English term in your writing, leave the punctuation as it was in the original language, rather than adding or removing hyphens to match the rules of hyphenation in English.
For example, always hyphenate the French term “savoir-vivre”, but never hyphenate the Latin term “a priori” – in both cases, following the style of the original language. If you’re unsure, check a dictionary.
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