When Hyphenation Is Unnecessary

A parrot, a cat, three dogs, a hamster, and a rabbit against a white backdrop.

Spotlight on CMOS 7.84

One of the main reasons to insert a hyphen between two words that aren’t normally hyphenated is to help readers sort out the text when those words are used as a compound modifier before a noun. For example, an apartment on the ninth floor of a building is a ninth-floor apartment; the added hyphen makes it immediately clear that ninth-floor is a single compound that modifies apartment.

Such hyphens make reading a little easier, but they also add a tiny bit of clutter to the page or screen. When comprehension isn’t threatened, they can often be left out.

The Case of the ‑ly Adverb

The classic example of when not to hyphenate a compound modifier involves ‑ly adverbs, like beautifully in the phrase beautifully behaved dog. The logic is that because beautifully is an adverb—and obviously so, thanks to that ‑ly ending—readers won’t need any help figuring out what modifies what.

There’s no such thing as a beautifully dog, not to mention a behaved dog that’s beautifully. So there’s no chance of a misreading.

This logic works well with Chicago style, which favors a “spare” approach to hyphenation, as described in the intro to the hyphenation table at CMOS 7.89. The gist of this approach is that when neither the dictionary nor the hyphenation table provides an answer, a hyphen should be added to a compound that doesn’t normally include one “only if doing so will prevent a misreading or otherwise significantly aid comprehension.”

In an earlier and somewhat more elaborately punctuated age, however, compounds modifiers formed with ‑ly adverbs tended to get hyphens, as the following examples demonstrate:

In spite of her deeply-rooted dislike, she could not be insensible to the compliment of such a man’s affection. (Jane Austen, Pride and Prejudice, vol. 2 [London, 1813], 124)

. . . namely, the highly-prized spermaceti, in its absolutely pure, limpid, and odoriferous state. (Herman Melville, Moby-Dick; or, The Whale [New York, 1851], 378)

Her discretions interested him almost as much as her imprudences: he was so sure that both were part of the same carefully-elaborated plan. (Edith Wharton, The House of Mirth [New York, 1905], 6)

The point of resurrecting those dusty old examples is to show that adding a hyphen to an ‑ly compound isn’t the worst idea. Those words, after all, belong together.

But the earliest edition of CMOS, published one year after The House of Mirth first appeared, ruled against such hyphens (see 1st ed. [1906], ¶ 167). And according to the latest edition of CMOS and many other modern guides, even the most meticulously edited text can do without them (see CMOS 7.86).

Established Open Compounds

Extending the example of ‑ly compounds, a hyphen can often be omitted from other types of compounds that present no risk of a misreading. For instance, the unhyphenated examples in CMOS 7.84public welfare administration and graduate student housing—are perfectly clear as written.

That’s at least partly because both “public welfare” and “graduate student” are familiar as open compounds—​especially in the context of administration and housing. It wouldn’t be wrong to add a hyphen to either of those compound terms (see CMOS 7.85), but it’s unnecessary.

If you’re faced with a compound modifier that seems to work just as well without a hyphen as with, but you’re not quite sure, check the dictionary. If the term is listed there as an open compound, the hyphen can probably be left out; otherwise, go ahead and add one.

For example, the phrase high school diploma (no hyphen) seems just as clear as high-school diploma (hyphen); not only is high school diploma a familiar phrase, but you’d have to make an effort to misread it. And the term high school is listed in Merriam-Webster as an unhyphenated noun, so in this case the hyphen can be left out.

Common usage, moreover, clearly favors not using a hyphen in such a phrase, even in published books, as this n-gram from Google Books shows:

Graph from Google Ngram Books Viewer comparing the prevalence of "high school diploma" with and without a hyphen in "high school" in books published since 1900.

But in less clear-cut cases, a hyphen will usually be the better choice. For example, the term high drama is entered as a noun in Merriam-Webster, but it’s not all that commonly used as a modifier. So a phrase like high-drama situation is best hyphenated in accordance with CMOS 7.89, section 2, under “adjective + noun.” And in some cases, dictionaries will list a hyphenated adjective form—as with high fidelity (n.), high-fidelity (adj.).

How Small Is That Animal Hospital?

Sometimes a hyphen in a compound modifier does more than simply make reading a little easier—it provides essential information. Take the example of a small-animal hospital. Without a hyphen, the phrase might easily refer to a small hospital for animals. With a hyphen, the phrase clearly refers to a hospital for small animals.

And that’s what we’d recommend—in general contexts (see also CMOS 5.92).

But let’s say you’re writing or editing an article for the Veterinary Journal, a peer-reviewed scientific journal established in 1875. Here are a few excerpts from “Effect of Attire on Client Perceptions of Veterinarians,” by E. Bentley, H. Kellihan, C. Longhurst, and R. Chun, from volume 265 (2020):

Clients volunteered to answer a survey in the small animal waiting area over a 3-month period.

Only three studies have examined veterinarian attire and client perceptions in veterinary medicine. In the first, 154 clients of a 24-h small animal emergency clinic were surveyed about their preferences of dress for veterinarians in a variety of situations.

Respondents were recruited by signs placed in the University of Wisconsin Veterinary Care (UW Veterinary Care) small animal hospital waiting area.

The Veterinary Journal isn’t averse to hyphens, as this sentence from the same article’s introduction shows (not to mention the modifiers “3-month” and “24-h” in the examples above):

The purpose of this study was to do a large-scale survey of the clientele of an academic teaching hospital to determine the influence of attire on client perceptions of veterinarian competence and comfort with veterinarians.

The point is that in this journal—one in which “small animal” is a frequently used phrase that has a specialized meaning (think cats, dogs, hamsters, etc.)—the hyphen simply isn’t considered necessary. Everyone—meaning anyone who would read something in a veterinary journal (and not only those who are members of the British Small Animal Veterinary Association)—knows what “small animal hospital” (or clinic or whatever) means.

But in more general contexts, a hyphen is more likely to be used, as in the journal PET Clinics. (Note that PET stands for “positron emission tomography”—an imaging technology that can be used on both humans and animals. The acronym doesn’t have anything to do with pets.)

In the 2020 article “Advances in Preclinical PET Instrumentation,” by Mahsa Amirrashedi, Habib Zaidi, and Mohammad Reza Ay, which investigates the use of PET scanners on small animals, the phrase “small animal” is hyphenated as needed:

Salient progress and considerable advances in small-animal PET imaging has had and will continue to have a far more profound effect on drug development and biomedical research.

The IRIS PET from Inviscan (Strasbourg, France) represents the latest generation of commercial small-animal scanners operating either in rotating or stationary modes.

The other key factor that should be taken into account when devising a small-animal scanner is the shape of the detector arrangements.

Those hyphens help readers who aren’t necessarily immersed in the world of small-animal care understand that we’re talking about small animals, not small scanners.


When in doubt about whether you should add a hyphen to a particular compound modifier before a noun, lean toward hyphenation, which is never wrong. But to avoid cluttering your documents with unnecessary hyphens, consider what works best in any given context—while also consulting the hyphenation guide in CMOS and the dictionary entries from Merriam-Webster.

Any small animals in your life probably won’t appreciate your attention to detail, but human readers just might.

Group of small animals by New Africa / Adobe Stock.

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2 thoughts on “When Hyphenation Is Unnecessary

  1. My bugbear is the used bookstore or even second-hand bookstore. The store is not pre-owned, as sellers of used cars put it. Is it a used-book store?

  2. I imagine that in the following sentence, the lack of hyphen in “high school student” could lead to ambiguity: “The high school student got busted for lighting up in the courtyard.” LOL

    As a copyeditor, I often struggle with hyphenation, so I appreciate this helpful article. Thank you for writing it.

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