A hyphen (-) is a punctuation mark used as a joiner. A hyphen is typically used to join the separate parts of a compound word to make it clear that it is one entity. (A compound word is a word made up of more than one word.)

Hyphens are seen:
  • In compound adjectives (e.g., I wrote a three-page document.)
  • In compound nouns (e.g., I asked a passer-by.)
  • In compound verbs (e.g., They will spot-check the passengers.)
  • In prefixed words (e.g., Please re-enact the crime.)
  • In fractions and numbers written in full (e.g., What's one-third of twenty-one?)
  • With list items that share a common second element (e.g., The two- and three-bedroom flats will increase in value four- or fivefold.)
  • At the end of a line to split a word that is too long to fit. (e.g., This is rare nowa- Days because modern word processors adjust the space between words to avoid it.)

Examples of Hyphens in Compound Adjectives

A hyphen joins the words in a compound adjective. (A compound adjective (shown in bold below) is a single adjective made up of more than one word.)
  • free-range eggs
  • six-foot table
  • two-year-old child
  • far-too-chatty individual
  • My single-minded aim is to give existence to fantasy. (Claes Oldenburg)
  • There's a difference between a free market and free-for-all market. (Bob Menendez)
There is an entry on compound adjectives.

Examples of Hyphens in Compound Nouns

A hyphen can be used to join the words in a compound noun. (A compound noun is a single noun made up of more than one word. Some compound nouns are hyphenated.)
  • a paper-clip
  • a six-footer
  • a two-year-old
  • cooking-oil
  • History is full of times when the inevitable front-runner is inevitable right up until he or she is no longer inevitable. (Martin O'Malley)
  • Behind every successful man stands a surprised mother-in-law. (Hubert H. Humphrey)
Lots of compound nouns are unhyphenated (i.e., one word), and some are two words.
  • wheelchair
  • hot dog
There is an entry on compound nouns.

Examples of Hyphens in Compound Verbs

A hyphen can be used to join the words in a compound verb, especially verbs formed from two nouns.
  • To gift-wrap
  • To ice-skate
  • I was court-martialled in my absence and sentenced to death in my absence, so I said they could shoot me in my absence. (Irish playwright Brendan Behan).
  • (Here, court-martialled is from the verb to court-martial.)
Compound verbs are far less common than compound adjectives and compound nouns. They are often invented by the writer to add a bit of flair or fun.
  • She will eyebrow-beat him into submission.
  • He cold-shouldered me when I was fist-pumping his team mates.
  • Remember, not all verbs comprising two words are hyphenated. Do not use a hyphen with a phrasal verb. (A phrasal verb comprises of a main verb and a preposition or particle, e.g., to break out, to drop off.)
  • Never give in, and never give up. (American politician Hubert H. Humphrey)
  • (Give in and give up are phrasal verbs. Phrasal verbs are not hyphenated.)
There is an entry on phrasal verbs.

Examples of Hyphens in Prefixes

A hyphen can be used to join a prefix to a word.
  • ultra-expensive
  • re-establish
  • co-opt
Most prefixed words are unhyphenated
  • cooperate
  • defuse
There is an entry on prefixes.

Examples of Hyphens in Fractions and Numbers Written in Full

Hyphens are used in fractions written out in full.
  • one-third
  • two-thirds
  • four-tenths
Writing a fraction in full means writing the numerator (the top number) and the denominator (the bottom number). Nouns like eighth, quarter, third and half don't get a hyphen.
  • A third of our food comes from pollinating plants. (Film director Louie Schwartzberg)
Hyphens are used in all numbers between 21 and 99 (less those divisible by 10) when they are written in full.
  • fifty-one
  • two hundred thirty-four
  • three thousand five hundred sixty-seven
You might be wondering why there is no and before thirty-four and sixty-seven. It is common practice to omit the word and (even though you might say it) because for many (especially Americans) and denotes a decimal point. In other words, they will take seven hundred and twenty-four as 700.24 not 724. (Interestingly, if you follow this practice and start writing out all the numbers from zero, you will reach 1000 before you use the letter a.)

Examples of Hyphens with List Items Sharing a Common Second Element

A hyphen can be used before a common second element in all but the last word in the list.
  • You can buy a two-, five- or seven-seater version of this car.
  • Would you like the one- or two-year plan?
These two examples show this technique with compound adjectives, which would ordinarily contain hyphens if written out in full. However, this technique can be used with compound words that wouldn't ordinarily contain hyphens.
  • I know who you are, Mr Clayderman. You could be Super-, Bat- or Spiderman.
    You'd still be late.
  • It will increase two- or threefold.

Examples of Hyphens Splitting Words at the End of a Line

If you find yourself using a hyphen to split a word at the end of a line to make it fit neatly, then change your word processor. It'll be worth it because the rules for splitting words (called hyphenation) are complicated. Worse. The rules for hyphenation often contradict each other, and the style guides are inconsistent. There's some good news though. If you rely on your instinct to split the word, you'll probably place your hyphen correctly because you'll place it at a natural split in the word (e.g., after a prefix or before a suffix). That said, here is a simplified version of the main rules that will see you through 82.4% of situations:
  • Break words at morpheme boundaries (e.g., un-touchable or untouch-able).
  • (A morpheme is the smallest grammatical unit. Prefixes, word roots and suffixes are morphemes. For example, in untouchable, the morphemes are un, touch and able.)
If your word doesn't have any obvious morpheme boundaries, then place your hyphen before a new syllable while adhering to the following (if relevant):
  • Break words between doubled consonants (e.g., lit-tle).
  • Do not separate a digraph (e.g., con-stant not cons-tant).
  • (A digraph is two letters representing one sound, e.g., ch, gh, ng, ph, qu, sh, th.)
  • If there is a string of consonants between syllables, insert a hyphen into the string as far left as possible (e.g., mon-strous).
  • 82.4%-ish.

Why Should I Care about Hyphens?

A hyphen is typically used to show that the joined words are a single entity (e.g., a single adjective or a single noun). This has the following benefits:

(1) It makes your text easier to read.
(2) It removes the possibility for ambiguity.
(3) It showcases your writing skills a little.

Here are five noteworthy points related to hyphens.

(1) Use a hyphen if the unhyphenated version of a compound adjective would be ambiguous

Your British readers will expect you to use hyphens to link the words in your compound adjectives, but, in the US, readers are more lenient. It is common to see compound adjectives without hyphens in both the UK and US conventions, especially with well-established terms that are unlikely to make a reader stall (e.g., ice cream stall, twentieth century building). So, it's not a serious error to omit the hyphen from a compound adjective. That said though, when the unhyphenated version of a compound adjective is ambiguous, you must use a hyphen to link its words.
  • a small business grant
  • (This is ambiguous. Does this mean a small grant for business purposes or a grant for a small business?)
  • a small-business grant
  • (This is not ambiguous. The hyphen makes it clear this is a grant for a small business. It could be a large grant.)
  • I have a concealed weapons permit.
  • (This is ambiguous. Does this mean a permit for concealed weapons or a permit hidden from view?)
  • I have a concealed-weapons permit.
  • (This is not ambiguous. The hyphen makes it clear this is a permit for concealed weapons.)
This is covered in more detail in the entry on compound adjectives.

(2) Don't use hyphens with adverbs that end -ly

When using an adverb to modify an adjective (e.g., perfectly formed ring), some writers feel the need to use a hyphen (e.g., perfectly-formed ring). With adverbs ending -ly (which is most of them) and the word very, that's a mistake.
  • It is a wonderfully-decorated tree. [wrong]
  • Paula is a very-talented student. [wrong]
This applies only to adverbs ending -ly. It does not apply to adjectives ending -ly.
  • It's such a friendly-looking place you can tell it's a family-run business. [correct]
  • (Friendly and family are not adverbs.)
It also does not apply to adverbs that can be used as adjectives (e.g., well, fast, best). When used as adverbs to modify an adjective, these words are hyphenated to avoid any ambiguity.
  • Lee is the best-known player on the pitch.
  • (Here, Alan is known better than any other player. Best is an adverb.)
  • Lee is the best known player on the pitch.
  • (Most people would take this to mean the same as the one above, but it could feasibly mean that Lee is the best player of all the known players, in which case best would be an adjective. If you're not following this point, substitute the word known with chubby, and best will stand out more clearly as an adjective.)
This issue crops up most commonly with the adverb well, which can also be an adjective meaning healthy.
  • Jack is looking for a well-fatted calf.
  • (The hyphen tells us that well is an adverb, making it clear that Jack is looking for a nicely fatted calf not a healthy fatted calf.)
This guidance will see you right: Use a hyphen with well when it's modifying an adjective. The likelihood of you wanting well the adjective is pretty low. (If you're not a gambler, substitute your well with healthy, and if your sentence makes no sense whatsoever, put well back in and use a hyphen.)

(3) When using an expression like three-and-a-half, don't join your adjective to your noun with a hyphen.

When used as compound adjectives, expressions like three-and-a-half and two-and-a-quarter are often hyphenated to make it clear they're one entity. If you decide to use hyphens in such a term, don't join your adjective to your noun with a hyphen.
  • He wants four-and-a-quarter-billion. [wrong]
  • He wants four-and-a-quarter billion. [correct]
  • (Here, four-and-a-quarter is a compound adjective modifying the noun billion. Joining them with a hyphen would be as wrong as He wants a nice-car.)
Be mindful, however, that your compound adjective might not end when the expression like four-and-a-quarter ends.
  • He wants four-and-a-quarter-billion dollars. [correct]
  • (Here, four-and-a-quarter-billion is the compound adjective modifying the noun dollars. This time, the hyphen between quarter and a billion is correct because billion is now part of the same compound adjective.)
Be particularly careful to group all the parts of your compound adjective when writing ages.
  • She is a twenty-four-year-old woman. [correct]
  • (All too often, the hyphen after year is mistakenly omitted. This is covered more in the entry on compound adjectives.)

    (4) Use your spellchecker smartly to spell compound nouns correctly

    Some compound nouns are one word (e.g., snowman, aircraft). Some compound nouns are two words (e.g., fish tank, cell phone). Some compound nouns are hyphenated (e.g., know-how, runner-up. And, some compound nouns have more than one acceptable spelling (e.g., paper clip, paper-clip and paperclip).

    Your spellchecker will not test the two-word version or the hyphenated version as a single entity. In other words, it will not highlight air craft or air-craft as an error (even though it should be aircraft). So, you have to test the one-word version. If your spellchecker doesn't like the one-word version, you then have a choice between the two-word version and the hyphenated version. Often, this really is your choice. You should use a hyphen for clarity (i.e., to make it instantly obvious it's a single entity) and to eliminate ambiguity.
    • pen friend / pen-friend
    • (The hyphenated version is clearer. It stands out as a single entity, making it easier to read.)
    • cooking oil / cooking-oil
    • (The hyphenated version makes it clear the oil is not cooking.)
    This is covered in more detail in the entry on compound nouns.

    (5) Use your spellchecker and your instinct to determine whether to use a hyphen with a prefix

    If you're unsure whether to use a hyphen with a prefix, start by not using a hyphen. However, use a hyphen if the unhyphenated version:
    • Looks too unwieldy for your taste (antiaircraft might be an example).
    • Is highlighted as spelling mistake by your spellchecker (e.g., reestablish).
    • Is ambiguous (e.g., Re-cover the sofa is not ambiguous, but Recover the sofa is ambiguous.)
    This is covered in more detail in the entry on prefixes.

    Key Points

    • Use hyphens in compound adjectives, compound nouns and compound verbs so your readers don't stall during reading.
    • Use hyphens in compound adjectives to eliminate any ambiguity.
    • Use hyphens in compound words so your readers think you're an on-the-ball cookie.
    • Don't link your compound adjective to the noun being modified.
      • He received a 2-year-sentence. [wrong]
    • Don't link adverbs ending -ly or very to an adjective.
      • It's a beautifully-carved frame. [wrong]
    • Before you put a hyphen in a compound noun, use your spellchecker to make sure it's not acceptable as a single word.
    • Don't use a hyphen after a prefix unless your spellchecker tells you to or you can't bear how it looks without a hyphen.
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