If you have been sane far too long, and you miss the old days of total insanity, ponder why the Oxford American Dictionary would approve this sentence:
The half-truth is that the halfback’s running was halfhearted, but the half-wit, who is half-baked, went off half-cocked, and drove the half-track, halfway, for a halfpenny, with his fly at half-mast.
This is why Fowler begins his discussion of hyphens, “No attempt will be made here to describe modern English usage in the matter of hyphens; its infinite variety defies description.” Even Lynne Truss, in Eats, Shoots & Leaves, concedes, “In the end, hyphen usage is just a big bloody mess and is likely to get messier.”
THE EASY PART – NUMBERS
We use hyphens to separate non-inclusive numbers like phone numbers and Social Security numbers; and to separate compound numbers, twenty-one to ninety-nine.
THE HARD PART – COMPOUND WORDS
Fowler explains: “The primary function of the hyphen is to indicate that two or more words are to be read together as a single word with its own meaning.” Churchill once wrote that the hyphen was “a blemish to be avoided wherever possible,” but he added, “except when nature revolts.” Here’s when nature revolts: extra marital sex, the five hundred odd members of the House, a little used car, the nine-millimeter gun owner, small business women. Although a missing hyphen will sometimes help the rest of us get through the day and provide "likes" on our FaceBook page when we circulate it to our seven thousand closest friends, a hyphen properly placed can avoid ambiguity and absurdity.
two or more words must be read as one noun
Dictionaries usually hyphenate for a few decades and then drop the hyphen. Pullover, breakthrough, and holdup all used to be compounds joined by hyphens. Here, you try it; put this hyphen “-“ anywhere you please in this sentence:
On the Isle of Skye, a short distance from the lodge, sits a large moor reserved for shooting visitors.
two or more words must be read as one adjective
Red-hot, dark-blue, white-haired, sky-high, snow-packed, easy-going, nice-mannered, battle-scarred, backed-up, door-to-door, up-to-date. Here’s another hyphen “-“ to try again:
As we neared the point, we saw a man eating hammerhead.
a prefix must be attached to a word
Nonsense has been combined, but non-stop has not. Postscript has arrived, but post-mortem isn’t there yet. Why bystander but not by-product? Generally, use a hyphen with prefixes ex, self, all, un, anti, pro, quasi, and the suffix elect. If any prefix appears before a proper noun, always hyphenate: un-American.
The prefix re sometimes needs a hyphen: re-enter; and sometimes does not: rewrite. But each version can mean something different: re-formed and reformed; re-mark and remark. We use the hyphen to clarify.
Except for the Hard Rules below, you likely will not make a mistake by hyphenating or refusing to hyphenate, unless what you write is absurd or ambiguous.
Hyphenate an adverb followed by an adjective where the two modify a noun: the now-retreating tide. However, as Churchill pointed out: “Richly embroidered seems to me two words, and it is terrible to think of linking every adverb to a verb by a hyphen.” Within that comment lies a little-known grammar rule: Hyphenate an adverb followed by an adjective, UNLESS the adverb ends in ly.
“A well-dressed man” is correct; “a nicely-dressed man” is not.
Hyphenate a compound modifier if it appears before the noun; but do not hyphenate it if it appears after the noun: “hard-to-find MG parts” is correct; but “MG parts are hard-to-find” is not.
Sometimes you can avoid hyphens by replacing them with prepositions: “half-hour intervals” could become “intervals of half an hour.”
When the first word of a compound is one of two alternatives, leave the first hyphen open: “Our hybrids include both hand- and machine-made parts.” Or repeat the second half: “Our hybrids include both hand-made and machine-made parts.” When the first hyphen is left open, it is called a “suspensive” hyphen. but in a job interview, reveal this information only if you prefer to remain unemployed.
If you’re not sure whether to hyphenate, use a fairly recent edition of a reliable dictionary. But remember that what appears with a hyphen in a Webster’s 30 years ago might appear in a new Webster’s as one word.