The guidelines for hyphenation are complex and inconsistent. At least copyeditors are kept in business, but it can be frustrating for a writer to understand when to hyphenate and when not. Hyphenation errors are among the most common spelling problems I see. Yes, spelling. Hyphens are often thought of as punctuation, but matters of hyphenation are correctly classified under spelling, as they are in Proofreading Secrets of Best-Selling Authors and The Chicago Manual of Style. At the risk of sounding like your mother, most of what you need to know about how to spell a word can be found by looking it up in a dictionary. Chicago recommends Merriam-Webster’s Collegiate Dictionary.
Compounds may be spelled in three ways: open, hyphenated, or closed. Open compounds appear in a single dictionary entry. Yes, you can look up make and then up, but you can also look up make up. If you do, you’ll see it’s a verb. Makeup is a noun. The hyphenated form make-up is not dictionary listed and would appear only if you needed an adjectival form.
I often see constructions like this: She put on her make-up. But try to look up make-up and you will be directed to choose make up or makeup or some other word.
Make up as a verb has several meanings. Makeup as a noun also has quite a few, including the sense of cosmetics. So you would write She put on her makeup. You might sometimes see the verb form hyphenated when it’s used as a modifier, e.g., He took a make-up test. But one of the noun senses of makeup is a test “in which a student may make up for absence,” so He took a makeup test would be acceptable, and is the far more common form.
If you’re not sure whether a word requires a hyphen or not, look it up.
Prefixes and Compound Modifiers
One of the places English gets most confusing is in the realm of compound modifiers. You would think that the adjectival phrase would be hyphenated wherever it appears, but no. It is hyphenated only before the noun, but not after: The wind was ice cold but the ice-cold wind. This is a very general rule and there are exceptions. For example, the term well-being is a hyphenated compound and will therefore always be hyphenated: He taught a well-being seminar and He taught a seminar about well-being.
The Chicago Manual of Style contains a ten-page chart of hyphenation guidelines, and it still doesn’t cover every possible English construction. Nevertheless, it will cover almost every possibility, so it’s worth grabbing.
Pay particular attention to the rules for prefixes. Most of the time, prefixes such as non, pre, post and semi do not require a hyphen. A prefix, by definition, may be joined to just about any English word. Yet your spell checker will not contain an ad hoc construction like I was semiexhausted, and will flag it as misspelled. It will probably prompt you to insert a space, but that will look wrong, so you’ll stick a hyphen in and call it good. But in Chicago style, semiexhausted would be the correct form. Spell checking software doesn’t know everything.
And, of Course, an Exception
Because this is English, it can’t just end there. Because compound modifiers are hyphenated, you might be inclined to hyphenate a phrase like duly-noted additions. But adverbs ending in -ly are the exception to the hyphenation rule. So it would be duly noted additions. Note that not all -ly words are adverbs, so family-owned business would still be hyphenated. Unless you write The business was family owned.
At about this point most folks are ready to throw in the towel. Hang in there. The rules are strange but not impossible to master. And if you really get fed up, you can always hire a copyeditor.