TWTS: A well-placed hyphen disambiguates when placed well
For anyone who's hoping for one exceptionless rule about when to use a hyphen, you may want to stop reading right now. That's What They Say isn't responsible for any disappointment incurred from this point forward.
Disclaimers aside, this week's question comes from a listener who thought there was a rule never to hyphenate adverbs when using a compound modifier. However, this listener says multiple websites have told them to hyphenate phrases like "densely populated city."
Many of us find ourselves taking pause over phrases similar to our listener's example, including English Professor Anne Curzan.
"Some of the colleagues who I draft documents with at the university hyphenate phrases like 'densely populated city' with a hyphen between 'densely' and 'populated,' but I don't,” Curzan says. “So, sometimes when we're working in these documents, we're having a little hyphen war where hyphens are going in and coming out, depending on who the most recent editor of the document is."
What we're talking about here is whether to use hyphens with compound modifiers — that is, modifiers with two or more parts, in this case, before a noun. Our listener's example "densely populated city" has an adverb and an adjective placed before a noun.
A compound noun can also be a modifier, as in “chocolate chip cookie.” You’ll notice we didn’t hyphenate “chocolate” and “chip.” That’s because “chocolate chip cookie” is fairly recognizable, i.e. it’s not ambiguous.
The advice that style guides give on whether to hyphenate is largely based on ambiguity and trying to disambiguate for readers. For example, “small-business owner” gets a hyphen so it’s clear that the business is small, not the owner. The same argument could be made for “much-needed clothing.” With the hyphen, it’s clear the clothing is much-needed. Without the hyphen, we could be talking about a large amount of needed clothing.
Of course, there are exceptions.
Many style guides will say don’t hyphenate when there’s an adverb with “ly” or when the word “very” is included. In the example our listener gave us, “densely populated city,” a lot of style guides would say a hyphen isn’t needed. That's because “densely” is an adverb and can only modify "populated," not "city."
However, some style guides argue that consistency is what’s important when it comes to hyphens and would advise you to go ahead and hyphenate: “densely-populated city.”
All that said, we hereby declare the aforementioned hyphen wars a draw.