Which is right: a backup plan, a back-up plan or a back up plan? How about a cutoff date, a cut-off date or a cut off date? A takeout menu, a take-out menu or a take out menu?
The answer: There is no answer. Technically, you could choose any of these forms and be correct. That's not to say that they're all equally good, obviously. But they're equally legitimate due to a weird little quirk of the language that occurs at the intersection of hyphenation rules and modifier rules.
Here's the basic idea.
Adjectives, which are a type of modifier, describe nouns: a large store, a nice day, an efficient employee. But in English we can use nouns the same way - to modify other nouns: a paint store, a vacation day, a government employee. We call this an "attributive" use, meaning a noun like "paint," "vacation" or "government" is attributing to qualities to another noun. In other words, it's a noun working as an adjective, which is standard and correct in English.
Hyphens are used in compound modifiers, a term that often means simply a multiword adjective: a guitar-making course, a good-looking man, a one-hand-washes-the-other arrangement. But the rules are loose.
In most of professional publishing, the rule is that you should insert these hyphens whenever they help, especially when a lack of a hyphen could create confusion or otherwise throw the reader off. My favorite example is illustrated in "a man-eating lobster" and "a man eating lobster." That's one case where a hyphen makes all the difference in the world. But others aren't as cut-and-dried.
For example, if I told you my uncle is an orange juice drinker, would you even momentarily wonder whether he's the kind of guy who enjoys all kinds of juice and whose skin just happens to be orange? Probably not. So hyphens are often optional, used at the discretion of the writer.
There are other rules governing hyphens. For example, a term that's spelled with a hyphen in the dictionary, like "good-looking," should probably always be hyphenated. Plus there are separate rules for prefixes and suffixes, as well as for compound modifiers that contain an "ly" adverb, like "a happily married couple." Terms like that aren't hyphenated.
But for our purposes all you need to know is that the writer can often use hyphens when forming compound adjectives.
Now, back to our backup/back-up/back up plan conundrum: Here's how these rules create a mess. The one-word "backup" is in the dictionary as a noun, as in "I need backup" or "When you save the file, create a backup." But the verb form is two words, "back up," as in, "You should back up that data immediately." Depending on which dictionary you check, the same is true cutoff/cut of, takeout/take out, checkup/check up, pickup/pick up and countless similar pairs.
So if you need an adjective, which should you use: the noun "backup" or the verb "back up"? And if you used the verb, would you hyphenate it?
On the former question -- no one -- offers any guidance. The dozens of style guides and grammar books I reference regularly contain nary a word on this matter.
They'll help you decide whether to hyphenate that two-word form, of course (most would say that "a back-up plan" is better than "a back up" plan because it's clearer). But not one will tell you whether you should have just used the one-word noun to begin with.
The experts I've discussed this with seem to prefer those one-word forms. Many would go with "a backup plan" over all other forms. But no one can tell you you're wrong if you don't.
June Casagrande is the author of "It Was the Best of Sentences, It Was the Worst of Sentences." She can be reached at JuneTCN@aol.com.