Hyphen (n.): the symbol (-) used to join words to indicate that they have a combined meaning or that they are grammatically linked, or to indicate word division at the end of a line.
There are two types of hyphen, both represented by the same horizontal line positioned mid height of the font used. One is a ‘soft’ hyphen and is used when a word is broken, for stylistic reasons, to fit on two lines. There are rules—that I won’t go into here—as to where a word can be split with a soft hyphen. The New Oxford Spelling Dictionary is one book that contains a list of where to split many words.
The other type of hyphen is a ‘hard’ hyphen. The use of the hard hyphen (referred to from now on as simply a hyphen) depends on many variables. The purpose of a word or phrase and its position in a sentence determine whether or not to use a hyphen, as does the chosen publishing style. It is therefore extremely important to be consistent with hyphens, whatever the style in which you are writing.
Remember, these guidelines apply to UK-English.
Compound Words and Hyphens
As explained in the en rule section, hyphens can be used to link two or more names together to make one name. For instance Saxe-Coburg-Gotha is one very English name.
A compound term (two or more words functioning as one word) can be ‘open’ (written as two or more words), ‘hyphenated’ (joined by a hyphen), or ‘closed’ (written as one word). There are many variations to be found in the guidance from well-known publishers. Both co-operate and cooperate are correct, but the Concise Oxford English Dictionary only gives the open ‘no one’ whereas the Collins Dictionary gives the option of the hyphenated ‘no-one’. This means that, according to your choice of dictionary, both of the following are correct: ‘No-one is re-creating a sense of co-operation’ and ‘no one is recreating a sense of cooperation.’ To further complicate matters, there is a tendency for hyphenated compounds to become closed ones as their usage becomes commonplace—a modern example is e-mail becoming email.
With all these personal-choice variables it’s important to consider why a hyphen should or should not be used. You’ll be pleased to know that there are some sensible guidelines.
Where you encounter a compound that contains a jarring of vowels or consonants, such as ‘part-time’, a hyphen is used to aid the pronunciation.
Hyphens can be used (or not used) to avoid confusion; in UK-English ‘full-time’ and ‘full time’ have different meanings and are fixed in their spelling. In US-English ‘full-time’ only takes a hyphen when it occurs before whatever it is describing; it behaves like a normal adjectival compound.
A compound that ‘modifies’ a noun, conveniently known as a compound modifier, takes a hyphen when it comes before the noun but not when it is placed after the noun. For instance, I wrote above: ‘There are many variations to be found in the guidance from well-known publishers.’ Here the compound (well known) is modifying the noun (publishers) before the noun has been mentioned, so it takes a hyphen. Had it been written ‘… in guidance from publishers that are well known’ then a hyphen would not have been needed. It’s the same with phrases such as ‘high quality’, ‘up to date’, and ‘17th century’: we have high-quality writing, and writing of a high quality; up-to-date equipment and equipment that is up to date; and even a mid-17th-century painting and a painting from the mid-17th century.
Do not use a hyphen with a compound where the first word is an adverb ending in ‘ly’, regardless of the compound’s position in relation to the noun being described. So we have ‘freshly baked bread’ (but ‘much-liked bread’). Two exceptions are ‘worldly-wise’ and ‘newly-wed’.
Using hyphens is all about removing ambiguity. ‘The state-of-the-art equipment’ and the ‘the equipment that is state of the art’ mean the same thing; ‘the state of the art equipment,’ however, depends on how the equipment has been cared for. Be careful not to clutter a piece of text with too many hyphens. ‘A heart rate monitor’ is clearly and unambiguously a monitor for measuring a heart rate, so there’s no advantage to comprehension by writing ‘heart-rate monitor’ or ‘heart rate-monitor.’
Some publishers distinguish between compounds that contain an adjective, such as ‘high energy’, and those compounds that are nouns, such as the ‘labour market’. In such a style ‘the high-energy labour market’ and ‘labour [no hyphen!] market redistribution’ would be correct.
Just in case that was all starting to make sense, let me chuck a spanner in the works. Compound adjectives (formed by combining an adjective and verb participle) are usually hyphenated, whether or not they are placed before or after the noun. Angelina Jolie is good-looking regardless of position, and—though the association of example eludes me—double-breasted suits are suits that are always double-breasted.
Hyphens with Compounds that are Nouns and Verbs
As a general rule of thumb use a hyphen when deriving a verb from an open compound noun, and for compounds containing a noun or an adjective that are derived from verbs. So from the open compound noun ‘[the] machine gun’ we get ‘the machine-gunner learned to machine-gun by practising with a machine gun’; and from ‘the indoor game’ we get ‘indoor-gaming’. When deriving from a verb we get ‘to blow-dry’ giving ‘the blow-dryer’; and from the verb ‘to blow glass’ we have ‘glass-blowing done by a glass-blower’.
When deriving a verb from a closed or hyphenated compound noun the verb is usually open: ‘The build-up to the workout was to build up confidence to work out with athletes.’
[Note: US-English tends to prefer a closed compound noun, so ‘the build-up’ becomes ‘the buildup.’]
But be careful as we have ‘to dry-clean the dry-cleaning’.
Phrasal verbs are almost never hyphenated.
Where you remain uncertain about using a hyphen it’s best to decide on one recognised style or dictionary and consistently follow the guidance given.
Paired (or Delayed) Compounds
When you encounter two or more consecutive and similar compounds it’s possible to avoid iterating the full terms and instead to omit the second part of all but the last term. So instead of ‘the second-placed contestant and the third-placed contestant will have a play-off’, we can have ‘the second- and third-placed contestants …’; or ‘a mixture of high- and low-quality work’; or ‘a two-, three-, or fourfold increase’. Whether or not you can add a word or words before the last term (‘fourfold’ in the last example), without iterating the previous term (threefold), is a matter of style. Consider the following: ‘a two-, three-, or with a little luck perhaps a fourfold increase.’
Compounds constructed from words beginning with capital letters are generally not hyphenated. We have Inland Revenue workers and Concise Oxford English Dictionary definitions. The exception, as mentioned previously, is with double-barrelled names.