A plaintive appeal appeared on Twitter:
So what’s the deal with hyphens? Are we dropping some of them?
I think this requires a clarifying piece from you. Some soothing enlightenment. (Stop snickering)
My writing group wants to know and I’m not up to the task.
Since you asked.
The first rule of the hyphen is that IT IS NOT A DASH. Don’t call it that.
The hyphen (-) links things, and the em dash (—), so called because it is the width of the capital letter M, separates things after the manner of commas and parentheses or indicates breaks in continuity.*
The most common question about hyphens is when to use them to link compound modifiers. Here are conventional patterns: adjective+hyphen+noun+noun. We write “red-hat crowd.” Or adjective+hyphen+participle+noun. We write “ill-conceived plan.”
Some adjective+noun compounds become such stock terms that we stop hyphenating them: “civil rights law” or “high school student.” Editors of the Associated Press Stylebook sparked a kerfuffle among editors in 2020 by declaring that “third grade teacher,” among other terms, no longer requires a hyphen.
English promiscuously allows nouns to modify other nouns, but we do not hyphenate them in the compounds familiar in corporate or bureaucratic cant: “content optimization strategy,” whatever that might be.
Adverbs ending in -ly are not conventionally hyphenated in compounds: “fully edited manuscript.”
There is also the question of hyphenating prefixes such as pre- and non-. The informed answer here is that sometimes you do and sometimes you don’t. Check the dictionary and stylebook you customarily use.
The main thing to keep in mind is that punctuation is never a matter of grammar. It is a mixture of conventions, which shift, and personal preferences, which vary widely. Some writers and editors are hyphen-happy, and some are averse. Really, you’re on your own. Follow your stylebook or your writer’s preferences up to the point at which they contravene clarity and common sense, and then stop.
* The en dash, (–) the width of the capital letter N, is commonly used in academic writing to indicate ranges, “the 1914–1918 Great War,” or scores, “Joe Biden’s 306–232 Electoral College victory.” AP style does not use the en dash at all. We’re not going further with the en dash because we’re talking about hyphens.