Today we’re discussing words with prefixes and whether we should hyphenate them. In general, English is moving away from hyphenation (it’s coworker, not co-worker, for instance), but there are some situations in which using the hyphen is the better course of action.

For this, I turned to the dog-eared, super-highlighted section 7.85 of my copy of The Chicago Manual of Style, which is my go-to resource for style questions. (Word style, not fashion style—I can handle the latter part on my own. Hellooo, silver combat boots!)

Here’s what the book says about prefixes.
A hyphen should appear:
1)   Before a capitalized word or a numeral, such as sub-Saharan, pre-1950
2)   To separate two Is, two As, or two other same vowels, such as anti-intellectual, extra-alkaline
3)   To separate other combinations of letters or syllables that might cause misreading, such as pro-life

(There are a few more rules; however, these are the ones you’ll most often experience, so let’s keep our focus here. And, as always, there are exceptions to the rules above, but we’re discussing what you should generally do.)

So, according to rule 1, it would be prewar, but pre-WWII (because of the capitalization).

According to rule 2, it would be extrasmart, but extra-academic (because of having the two side-by-side letter As).

Rule 3 is where it gets tricky to me. It basically says, if you think not hyphenating a word may cause people to misread it, then use a hyphen. Well, that’s open to interpretation of what one thinks may lead to a misread. The rule, according to The Chicago Manual of Style is: when in doubt, check Merriam-Webster. This means, if a word is not hyphenated in that dictionary, don’t hyphenate it.

In the last book I edited, I had a conundrum with words starting with rein (so the prefix re- and a word that started with the letters I and N.) For example, this morning I looked up the word reinvest, as in “to invest again.” To me, I see this word as two words smushed together: rein and vest. It looks (to me) like a noun that means “a vest you wear with your reins.” Like: “I wore my reinvest so I didn’t fall off my horse.” But, of course, that’s not its meaning. Yet, the lords at Merriam-Webster think people won’t have a problem misreading that word, so it shouldn’t get a hyphen.

I might lose my grammar police badge for this, but in the last book I edited, I used my own judgment (in some cases) regarding hyphenation. I encourage you to do this, too. If you think readers will be confused if you don’t use a hyphen, then use a hyphen. (But don’t tell anyone I told you that.)

Quiz
Decide if each word should be hyphenated. Keep in mind rules 1 and 2 mentioned above. (We’re not even going to get into rule 3 here because, as I mentioned, it’s too open to interpretation.)

1)   hyper active
2)   neo natal
3)   post 1984
4)   hyper sonic
5)   inner Chicago
6)   anti inflammatory
7)   non violent
8)   over zealous
9)   mega ambient
10)  co author

Answers: 1) hyperactive 2) neonatal 3) post-1984 4) hypersonic 5) inner-Chicago 6) anti-inflammatory 7) nonviolent 8) overzealous 9) mega-ambient 10) coauthor