Q: I’m puzzled about when words are hyphenated and when they aren’t. What’s the rule? Help!
A: The use of hyphens is a long and complicated subject, and Pat devotes a considerable section to it in her grammar and usage book Woe Is I.
There’s no single rule that covers all situations. But there is one rule (involving compound modifiers before a noun) that’s pretty straightforward.
In general, two-word descriptions are hyphenated before a noun (“powder-blue dress,” “red-haired cousin,” “well-done hamburger”). But if the description comes after the noun, no hyphen is used (“a dress of powder blue,” “a cousin who’s red haired,” “a hamburger well done”).
However, there are many exceptions!
Compound modifiers in which one of the words is “very,” “most,” “least,” or “less” (as in “most pleasing tune”) don’t have hyphens. And if one of the words ends in “ly,” there’s generally no hyphen (as in “incredibly difficult task”).
Some prefixes always take hyphens (as in “self-effacing,” “ex-husband,” “quasi-official”).
Others sometimes do and sometimes don’t (“pre,” “re,” “ultra,” “anti”). Hyphens appear in fractions (“two-thirds”) but generally not in whole numbers (“two hundred”) unless they’re compounds like “twenty-three,” “forty-six,” and so on.
Some compounds simply have to be memorized – or, better yet, looked up in the dictionary. For instance, hyphens appear in some family terms (like “brother-in-law”) but not in others (“half sister”).
In fact, “half” is all over the map as part of a compound: sometimes hyphenated (“half-moon,” “half-life”), sometimes separate (“half note,” “half shell”), and sometimes solid (“halfhearted,” “halftime”).
When you look words up, make sure you have a recent dictionary. Hyphenation may change from edition to edition.
Often nouns begin life as two separate words (like “home school” and “try out”), then become hyphenated words (“home-school,” “try-out”), and finally lose their hyphens as they become more common (“homeschool,” “tryout”).
We’ve written before on the blog about “homeschool,” “tryout,” and “cross” (a term that can be bewildering in compounds).
Both “half” and “cross” are great arguments for buying a dictionary, in case you don’t already have one.
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