The complexity of rules about those little dashes that separate many words for various reasons causes so much misunderstanding that many writers just leave them out of the recipe or spill them randomly into the mixing bowl. But your compositional cuisine need not be so undisciplined. The rules may seem complicated at first, but soon you’ll be able to put hyphens in their place.
Hyphenate two adjectives united to modify a noun: “a well-trained writer.” But do so only before the noun: “a writer who is well trained.” Keep in mind, though, a convention that has arisen in which permanent open compounds, words that have been bonded together to form perpetual concepts, like “income tax” or “ice cream,” don’t take a hyphen even in phrases like “income tax records” and “ice cream cone.”
How do you know which compounds have bonded and which remain free agents? If an open compound is listed in the dictionary, it’s permanent.
But notice that these rules apply to adjectives but not to a similar-looking class of words; adverbs ending in “-ly” aren’t hyphenated to the verbs they modify: “a brightly colored shirt,” “a quickly memorized poem.” But most other adverbs are (“little-known fact,” “best-kept secret”); compounds with “least,” “less,” “most,” and “more” are exceptions.
Nouns are usually compounded, too, of course (“footstep,” “mountaintop”) but some, like “life-form” and “mind-set,” resist the closure that most of their like have accepted. Compounds that can be used as verbs and nouns alike differ in that the former are often hyphenated (“I had to jump-start his car”) and the latter aren’t (“He asked me for a jump start”). Another example is “fast track”: “We fast-tracked the project,” but “It’s on the fast track.”)
4. Multiword Coumpounds
Multiword compounds like “right-of-way,” “back-to-back,” and “up-to-date” always include hyphens. Beware, though: “Head to toe,” although a common expression, does not appear in the dictionary with or without hyphens, so omit them (unless the phrase modifies a noun: “a head-to-toe inspection”). Familiar word strings that modify nouns are usually hyphenated before and after: “next-to-last person in line,” “the reply was matter-of-fact.”
5. Confusing Words
Some words in which you wouldn’t expect a hyphen to persist remain to avoid confusion with a similar word with a different meaning (“re-cover,” as opposed to “recover”; “re-creation” instead of “recreation”).
Had enough? We haven’t even covered every hyphen rule yet, but I’ll save some for later. The bottom line about this floating line, though, is: “When in doubt, look it up.”