To Hyphenate or Not to Hyphenate? Part I

If you're like the rest of us, you have a terrible time trying to remember when to hyphenate compound nouns. For example, why isn't air conditioner hyphenated if air-conditioning is? How does a person keep up when the rules are constantly changing and even the grammar authorities disagree about hyphen placement?

The Gregg Reference Manual (¶ 801-803) provides a few rules of thumb to help us out.¹ Here is a quick summary for your reference:

Compound nouns ending in these words are typically hyphenated:
In: break-in, check-in, drive-in
On: add-on, carry-on, run-on

Compound nouns ending in the these words are typically solid:
Down: breakdown, countdown (exceptions: put-down, step-down)
Out: blackout, burnout, hideout (exceptions: cop-out, falling-out)
Over: hangover, layover (exceptions: comb-over, once-over)
Back: feedback, hatchback, piggyback

Compound nouns ending in these words are solid or hyphenated:
Up: breakup, buildup, pileup―but also―cover-up, mock-up, tune-up
Off: kickoff, layoff, standoff―but also―drop-off, play-off, show-off

Confused yet? I am! The best advice I've heard is to keep a current dictionary handy―or bookmark your favorite online dictionary. If the compound noun doesn't appear in the dictionary as a solid or hyphenated word, it's a safe bet that the individual words should be separated.

Keep in mind that these rules only apply when the words are used as compound nouns, not as verb phrases. For instance, the words get together are treated differently depending on whether they are used as a compound noun or a verb phrase:

            Compound noun:  Let's plan a get-together.
            Verb phrase:  Let's plan to get together.

Next week we'll discuss a few additional rules of hyphen placement. In the meantime, keep those dictionaries close!

Additional Resources:

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Source:

1. Sabin, William A. The Gregg Reference Manual. Tenth Edition.
         New York: McGraw-Hill/Irwin, 2005, pp. 218-219.