Hyphens are used to link words and parts of words. They are not as common today as they used to be, but there are three main cases where you should use them:
Hyphens are used in many compound words to show that the component words have a combined meaning (e.g. a pick-me-up, mother-in-law, good-hearted) or that there is a relationship between the words that make up the compound: for example, rock-forming minerals are minerals that form rocks. But you don’t need to use them in every type of compound word.
noun + adjective
noun + participle
|adjective + participle|
With compound adjectives formed from the adverb well and a participle (e.g. well-known), or from a phrase (e.g. up-to-date), you should use a hyphen when the compound comes before the noun:
well-known brands of coffee
an up-to-date account
but not when the compound comes after the noun:
His music was also well known in England.
Their figures are up to date.
It’s important to use hyphens in compound adjectives describing ages and lengths of time: leaving them out can make the meaning ambiguous. For example, 250-year-old trees clearly refers to trees that are 250 years old, while 250 year old trees could equally refer to 250 trees that are all one year old.
Use a hyphen when a compound formed from two nouns is made into a verb, for example:
an ice skate
a booby trap
a spot check
a court martial
You should NOT put a hyphen within phrasal verbs - verbs made up of a main verb and an adverb or preposition. For example:
You should continue to build up your pension.
They broke in by forcing a lock on the door.
We stopped off in Hawaii on the way home.
If a phrasal verb is made into a noun, though, you SHOULD use a hyphen:
There was a build-up of traffic on the ring road.
The house was unoccupied at the time of the break-in.
We knew there would be a stop-off in Singapore for refuelling.
In the past, these sorts of compounds were usually hyphenated, but the situation is different today. The tendency is now to write them as either one word or two separate words. However, the most important thing to note is that you should choose one style and stick to it within a piece of writing. Don’t refer to a playgroup in one paragraph and a play-group in another.
Hyphens can be used to join a prefix to another word, especially if the prefix ends in a vowel and the other word also begins with one (e.g. pre-eminent or co-own). This use is less common than it used to be, though, and one-word forms are becoming more usual (e.g. prearrange or cooperate).
Use a hyphen to separate a prefix from a name or date, e.g. post-Aristotelian or pre-1900.
Use a hyphen to avoid confusion with another word: for example, to distinguish re-cover (= provide something with a new cover) from recover (= get well again).
Hyphens can also be used to divide words that are not usually hyphenated.
They show where a word is to be divided at the end of a line of writing. Always try to split the word in a sensible place, so that the first part does not mislead the reader: for example, hel-met not he-lmet; dis-abled not disa-bled.
Hyphens are also used to stand for a common second element in all but the last word of a list, e.g.:
You may see a yield that is two-, three-, or fourfold.
You can read more about when to use hyphens on the Oxford Dictionaries blog. Here you will find helpful tips on when to use hyphens and examples of when they should not be used.
Back to punctuation.
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