There’s nothing wrong with hyphenating “multi-cultural.” There’s nothing wrong with not hyphenating “multicultural.” There’s nothing wrong with doing it both ways in a single document.
But it’s very wrong to do it both ways in a single document you’re trying to pass off as well-polished writing.
In the world of professional publishing, there’s one thing that’s more wrong than being wrong: being inconsistent. And perhaps no element of editing creates more opportunities for inconsistency than prefixes.
Some prefixes use hyphens to attach to a word. Some don’t. Some work better with an en dash than a hyphen. Many have strict rules on whether to hyphenate them. Others leave it at your discretion. Still others are subject to rules that change depending on which editing style you want to follow.
Take “co-worker,” for example. Lots of places write it “coworker,” which is technically acceptable even though it conjures the idea of someone who spends 40 hours a week irking cows.
Book publishers don’t agree. Their resource guide, the Chicago Manual of Style, states expressly that “coworker” doesn’t take a hyphen. Neither does coauthor, coeditor or coequal.
Newspaper types see the prefix “co-” differently. “Retain the hyphen when forming nouns, adjectives and verbs that indicate occupation or status,” the Associated Press Stylebook advises, with examples that include co-author, co-defendant, co-host, co-star and co-worker.
But both styles agree that “coequal,” “cooperate” and “coordinate” take no hyphen.
I know what you’re thinking, but this is not a vast conspiracy to annoy writers. It’s just the result of different wordsmiths applying their best judgment about when a hyphen helps the reader see more quickly how the prefix is working.
Both styles agree that, as a rule, prefixes should not be hyphenated. But there are tons of exceptions. For example, have you ever seen anyone use “coopt” as a verb? Not likely. “Co-opt” is the preferred form because, as AP puts it, “a hyphen is used if a prefix ends in a vowel and the word that follows begins with the same vowel.” Chicago agrees.
So why don’t you see hyphens in “cooperate” and “coordinate”? Well, as we’ve seen when “good-bye” and “teen-ager” became “goodbye” and “teenager,” long-term use has the effect of closing up compounds, giving us hypertension, macroeconomic and cyberspace.
Lots of prefixes have special rules and, in many cases, the authorities disagree on what those rules should be.
Take “anti,” for example. “Antiaircraft” would be almost unintelligible without a hyphen: anti-aircraft. The same would be true of antigun, antieducation or antitelevision. That’s why AP says that most uses of “anti-” take a hyphen, with exceptions for words often found in dictionaries, like antibiotic, antidespressant and antithesis.
Chicago makes similar exceptions, but their blanket rule for “anti-” is the opposite of AP’s: In general, don’t hyphenate it.
Chicago style has a rule for attaching a prefix to a number, like pre-1950s. In that style, you don’t use a hyphen. You use an en dash, which is sort of halfway between a hyphen and a regular dash.
In AP, you use a hyphen to attach a prefix to a number. Yet both styles agree that these terms never end up closed forms like pre1950s. Punctuation is not optional here.
And you’ll never see antiAmerican, preE.U. or proNATO as a closed compound. Styles agree that when you’re attaching a prefix to a proper noun or anything that begins with a capital letter, that’s another case where you can’t drop the hyphen.
For lay users who don’t want to look up every prefix every time they need to use one, the simple rule is never hyphenate it unless the results are too weird looking. If you’re faced with an unsightly option like exhusband, unBritish or subsubparagraph, trust your eye and write it ex-husband, un-British or sub-subparagraph.