Saturday, January 23, 2010

Don't Fear the Hyphen

Hyphens come up a lot in scientific writing. Or at least they should. Unfortunately, small as they are, many people are afraid of them.

One problem is that hyphens get used for some very different purposes, although all of them tend to bind words or fragments together. I'm only going to talk here about making compound words with them.

Another problem is that you don't have to use a hyphen if you don't have to: if the meaning is clear without it (semantics), you're allowed to omit it (punctuation). This makes it very hard to figure out the real punctuation rules, since they don't arise from syntax alone.

Compound words are hard to predict. Sometimes two words are locked together to form one new word, as in German: eyewitness. Sometimes the two words keep their distance even as they form a single, new concept: eye shadow. But some pairs are bound with the medium-strength hyphen: eye-opener. This mostly happens when both words are nouns, so that the first noun is acting as an adjective, making the second more specialized.

There's really no perfect way to know which form is favored, and it varies over time. Novel pairings generally start out separated and become hyphenated when they seem to represent a unique combined identity. When that combined form becomes so familiar that it is easily recognized, the hyphen disappears, (unless the result would be confusing, as in a recent example, "muppethugging," or the less novel "cowriting.") You just have to look in an up-to-date dictionary.

For the single compound words and those that are always hyphenated that's the end of the story. The problem is that the isolated pairs of words sometimes should be hyphenated, too. This hyphenation is not a property of the pair, and it can't be found in the dictionary. It's a real punctuation mark, and depends on the details of the sentence.

The hyphen belongs when the pair is used as an adjective, known as a compound modifier, as in the previous "medium-strength hyphen." But generally the hyphen is omitted when the adjective occurs later on: "The hyphen has a medium strength." But the AP Stylebook (not hyphenated!) says that when that "after a form of to be, the hyphen usually must be retained to avoid confusion: The man is well-known." AP also has a rule that when for an adverb-adjective pair, the hyphen is not used if the adverb is "very" or ends in "-ly."

OK, this is getting confusing, so let's regroup: The important principle is that the hyphen is there to make clear when there is a link that might otherwise be missed. If we talk about a "highly important person," it's clear that it's the importance that's high, not the person. But if we talk about a "little known person," it's not so obvious whether it's the knowledge or the person that's diminutive, because
"little" can be an adjective or an adverb. If it's an adjective, you might have said "little, known person, " but "little-known person" avoids any chance of confusion.

The problem is worse when the first word is a noun, because it doesn't really give you any syntax clues about whether it's acting as an adjective or adverb. This issue comes up frequently in science writing. I imagine most people will realize that a "surface area calculation," refers to a calculation of surface area, and not a surface calculation of the area. But sometimes it's hard to know what will be confusing. I prefer to assume as little possible about what my readers are getting, so I would use "surface-area calculation." But many editors correct this (and I generally defer to them).

Unfortunately, there is a compelling to reason to be sparing with hyphens, which is that they can't be nested. This also comes up frequently in science writing, when a compound modifier is constructed from another compound modifier, as in "surface area calculation results." If we used parentheses to tie together related words, this would be rendered "((surface area) calculation) results." But there's no way to indicate priority with hyphens.

The right thing to do is to decide what level of compounding needs to be made explicit, and retain hyphens at all levels up to that, for example "surface-area-calculation results." Sadly, I frequently see something like "surface area-calculation results." That's just wrong, since the hyphen ties together "area" and "calculation" more strongly than "surface" and "area." In this case you'd be better off leaving out all hyphens and hoping for the best.

Of course, as in most cases of confusing writing, the best alternative is "none of the above": recast the sentence so that it doesn't have compound-compound modifiers. "The results of the surface-area calculation" leaves nothing to chance. But it's clunkier.


  1. Hi Don. I searched Google for "nested hyphenation" in trying to figure out how to write a certain sentence, and this page is the only relevant result that I found.

    In my example I went with the equivalent of "surface-area -calculation." What do you think of that solution? I think it looks okay and probably wouldn't be confused for a suspensive hyphen (just learned about that one). Although I have a second and better solution: to resurrect the double hyphen in a new role for nested hyphenation! Any idea how one would go about (re)introducing a grammatical symbol? :)

  2. Since I wrote this post, I have learned that the Associated Press has rules about using an en-dash (a dash with the typographic width of the letter "n," as opposed to the wider em-dash) to buy one extra level of hierarchy: "surface-area–-calculation results." This is the same idea as the double hyphen, and in fact I replaced the en-dash with a double hyphen here. In many fonts it's a pretty subtle distinction, though.

    The spaced-off hyphen might be OK, but it happens to break the line on my window so that "-calculation" is on the next line, which is confusing. Of course, software does a lot of odd things with hyphens already.

  3. Thanks for the response! That's great to know. Here it is with an en-dash: surface-area–calculation. I guess it's not very distinguishable with this font, though. (BTW if you have a Mac, Alt+hyphen produces an en-dash and Alt+Shift+hyphen produces an em-dash; I love that.)

    As for the double hyphen, it's not -- but more like =. You'll see if you click the link in my first post.

  4. Ron December 8, 2016 Come on guys, for the double hyphen print problem just hold down the Ctrl key and click 2 times on the minus key pad. Twice for the dash and in fictional use sometimes click three times for an extended pause..