5 Cases of Extraneous Hyphenation with Numbers

By Mark Nichol

The combination of numbers, spelled out or in numerical form, and hyphens is a volatile mixture that often confuses writers. Here are five sentences in which hyphens are erroneously inserted into constructions that do not require them, with explanations and corrections.

1. “Four-percent of adults may have ADHD.”
There’s no reason to combine four and percent. The writer might have incorrectly extrapolated from the use of fractions in the same type of construction (“One-third of respondents agree with the statement”), but the sentence should read, “Four percent of adults may have ADHD.”

2. “Astronomers say an object five-times bigger than Jupiter is the first planet outside our solar system to be imaged.”
The reference to the exoplanet’s magnitude of size in comparison to Jupiter requires no linking hyphen. The misunderstanding perhaps arises from the fact that “five times” modifies bigger, but bigger is an adjective, not a noun, and words combining to modify adjectives are not hyphenated. The correct form is “Astronomers say an object five times bigger than Jupiter is the first planet outside our solar system to be imaged.”

3. “This monk began his vow not to speak with a 2-1/2 year walk up the coast.”
Writers often erroneously insert a hyphen between a whole number and a fraction in a mixed fraction. It’s not necessary, but it is required between the mixed fraction and the noun that follows when they combine to modify another noun, as in this example: “This monk began his vow not to speak by taking a 2 1/2-year walk up the coast.” (2 1/2 is considered a single element, so omit the intervening hyphen.) Note, too, the slight revision to eliminate the suggestion that the monk conversed with a 2 1/2-year walk up the coast.

4. “The electrified border, 10-feet-high, is to be completed across the border with India.”
If this sentence used the phrase “10 feet high” as a modifier preceding “electrified fence” (“a 10-foot-high electrified fence”), the hyphens linking the elements as a unified description would be valid. But in a simple reference to physical dimensions, no hyphens are necessary: “The electrified fence, 10 feet high, is to be completed across the border with India.”

5. “You must have a keen sense of how to capture the attention of the 18-34 year-old news junkie.”
This sentence tries to observe the basic rule about connecting the numbers in a range (preferably with an en dash rather than a hyphen) but errs in its failure to recognize the special case of suspensive hyphenation that overrules that usage. The sentence refers to a demographic cohort consisting of 18-year-old news junkies and 34-year-old news junkies and all news junkies in between. When using a range involving a number compound, elide most of the first element, retaining only the number (spelled out or in numeral form) and a hyphen, followed by a letter space: “You must have a keen sense of how to capture the attention of the 18- to 34-year-old news junkie.”

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8 Responses to “5 Cases of Extraneous Hyphenation with Numbers”

  • thebluebird11

    Well, as has been discussed, if you are saying “Disney’s new flying plaything has been heavily hyped,” then no, there would not be a hyphen. But when the sentence is turned around and the phrase “heavily-hyped” is now an adjective modifying the plaything, I personally would stick the hyphen in there, -ly ending notwithstanding. Same thing for “seasonally adjusted.” If something is seasonally adjusted, that’s fine. But if something is done on a seasonally-adjusted basis, that is different. It now becomes an adjective (“On what kind of basis? On a seasonally-adjusted basis.”) Again, I could be wrong, but I have a feeling I will persist in sticking hyphens in these little spaces unless I am writing professionally and my editor whacks my knuckles with a ruler LOL

  • Sally

    Sorry to disagree with my namesake here, but like thebluebird, I would use the hyphens in the cases cited.

  • Mark Nichol


    Actually, the hyphen in “two-fifths” is correct even when the fraction is not modifying anything. There is, as far as I can tell, no reason for the hyphen to be there (a fifth is a thing, so it’s no different in construction than “two birds” or “two [anything else]”), but in this case, tradition has, as it so often does, trumped logic.

  • Lester Smith

    Excellent article, Mark! I’ve flagged it to be shared today via UpWrite Press’s Twitter feed and Facebook page.

    @Sally, in the case of adverbs ending in ly (seasonally, heavily), a hyphen is never used.

    For what it’s worth, although I write and edit professionally, I always recheck such things when proofreading. I go to Write for Business first (because it’s concise and covers most rules), then the Chicago Manual of Style for more esoteric or difficult questions.

  • Paul Goble

    In the last few years, I’ve noticed a sharp increase in the use of extraneous hyphens with numbers. The trend originated in broadcast writing, where hyphens after are used after numbers to facilitate reading the story aloud. But then those broadcast stories began appearing on the Web sites of various media outlets. Before long, other news writers started picking up the style. Meanwhile, newspapers were firing editors, and we began seeing stories printed right from the news wires without editing. Now the public at large, seeing those hyphens in writing from “reputable” sources online and in print, is beginning to think that the hyphens are correct and necessary.

  • thebluebird11

    @Sally: Are those hyphens wrong? I would put them there. I have not consulted a grammar or style guide, so of course you might be correct, but when I write, I feel I want to keep things as smooth as possible for the reader, so I want them to know, for example, that “seasonally-adjusted” is a concept, describing the basis (a noun) on which something occurred, and I think the hyphen helps them mentally absorb that faster than if it were missing. And, in your first example, “heavily-hyped” modifies “plaything,” (a noun), so I think a hyphen would be appropriate there, too. Again, I could be wrong. I think I might tend to over-use hyphens. Mark?

  • John White

    Another commonly misplaced (I think it’s misplaced) hyphen is in written fractions: “Two-fifths of the Marx Brothers died during the 1960s.” I believe there’s no need for a hyphen between “Two” and “fifths,” but I’m willing to be corrected.

    @Sally: I’m not Mark Nichol, but I think a hyphen after an -ly adverb is unnecessary.

  • Sally Bahner

    Good post on the numbers. I really thought that 2-1/2 would be hyphenated because of how easily it would be to run the numbers together.
    Speaking of hyphens, could you please address the use of hyphens with adverbs and adjectives in a daily post? It’s not even 10 a.m. and I’ve seen two wrong usages already. It’s becoming an epidemic, even in the most professionally (no hyphen) written articles!
    “This is Disney’s heavily-hyped new flying plaything…”
    “…but it’s down on a seasonally-adjusted basis…”
    At least “it’s” was used correctly here!

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