Using the hyphen
As an editor I spend quite a lot of time looking things up in the dictionary. The most common reason for me to do this is to check whether or not a word or phrase should be hyphenated.
The problem is, different dictionaries will give you different answers, and every style guide will helpfully inform you that there are no firm rules on whether you should run two words together, hyphenate them or leave them separate. For this reason, sometimes the best you can do is to be consistent in a given document. Sticking to the one dictionary and one style guide will certainly help.
However, if you understand the general reasons and principles behind hyphenating you will be ahead of most people. Hyphens help avoid ambiguity, making a text easier to read and understand. Here are some guidelines based on style manuals commonly used in Australia:
Prefixes
English is awash with prefixes that alter the meaning of the base word. Many prefixes are simply tacked straight on to the word (misunderstanding; dislike), but others need a hyphen to avoid confusion:
Janacek decided to re-cover the old sofa in order to recover its bohemian charm.
Estelle will re-sort her collection of seashells while holidaying at a Mediterranean resort.
Sometimes a hyphen is used to avoid putting two vowels together (pre-empt rather than preempt; anti-aircraft rather than antiaircraft). Hyphens are also useful in the electronic world: e-book rather than ebook; e-commerce rather than ecommerce.
If the base word needs a capital letter, italics or quotation marks, use a hyphen:
It was considered un-Italian to have an anti-Risorgimento attitude.
Compound words
Some combinations of two or more words start out as separate words, then hold hands with a hyphen, and eventually tie the knot (tool kit, tool-kit, toolkit). So an older dictionary might differ from a more recent edition (colour-blind or colourblind? cease-fire or ceasefire? bitter-sweet or bittersweet?).
Compound adjectives that are set phrases are not usually hyphenated, except to avoid ambiguity (the tax office ruling was challenged by a foreign-office lackey). Where the first word ends in ly, a hyphen is generally not used (a thoroughly annoying habit; a highly regarded scientist).
Line breaks
If you must use a hyphen to break a word that won’t fit on one line, there are a number of rules: don’t break a one-syllable word, and avoid breaking a two-syllable word; take at least three letters down to the next line (lust/fully not lustful/ly); avoid ambiguity (loop/hole not looph/ole; draw/ings not dra/wings).
Aarrgghh—confusion!
Editors do bang on about consistency, but sometimes two apparently identical expressions are not identically hyphenated. Compound adjectives (normally appearing before a noun) sometimes look the same as adverbial phrases (usually coming after a verb), but only the former might need hyphenating:
I want an up-to-date report on this project; please keep all the filing up to date while I’m overseas.
That particular politician is a well-known liar; Kylie is well known in the music industry.
It is said that the Oxford University Press style manual used to warn: ‘If you take hyphens seriously, you will surely go mad’.
See also: