Writers are easily confused by, or are negligent about, proper use of hyphenation with phrases with numbers, whether the numbers are represented in spelled-out or numeral form. The following sentences represent various types of erroneous use of hyphenation; a discussion after each one points out the problem, and a revision resolves it.
1. In April 2016, the Houston area was soaked by a once-in-10,000 years rainfall event.
This sentence, which refers to a rainfall event of the type that occurs once in 10,000 years, includes a phrasal adjective representing that frequency, and year is part of the phrase, so it must be connected to the rest of it: “In April 2016, the Houston area was soaked by a once-in-10,000-years rainfall event.” Alternatively, the statement can be relaxed (and rendered less cluttered and easier to read) by converting the phrasal adjective to a modifying phrase that follows “rainfall event”: “In April 2016, the Houston area was soaked by a rainfall event of the kind that occurs perhaps once in 10,000 years.”
2. In last year’s survey, 43 percent of 40-49 year-olds reported using the bank’s app.
Here, as often, an attempt at suspensive hyphenation, in which one or more words is elided when two equivalent terms can share a supporting word or phrase common to them, has gone awry. The full version of the descriptive phrase is “40-year-olds to 49-year-olds,” and the omission of the first instance of “year-olds” should result in the following rendering: “In last year’s survey, 43 percent of 40- to 49-year-olds reported using the bank’s app.” (If a publications style dictates spelled-out numbers, the correct treatment is “In last year’s survey, 43 percent of forty- to forty-nine-year-olds reported using the bank’s app.”)
3. We expect to complete the project within the next five-to-ten years.
The number range in this sentence is incorrectly styled due to a writer’s mistaken belief that because a range is involved, one or more hyphens belong in there somewhere. What is required, technically, is an en dash (–) rather than a hyphen (-)—but only if the numbers are treated as numerals: “We expect to complete the project within the next 5–10 years.” (Some publications, including many newspapers, dispense with the en dash and use a hyphen in such cases, but most books and magazines employ it; usage online and in other print media varies.) When the numbers are spelled out, no connective symbols are required: “We expect to complete the project within the next five to ten years.”
I disagree with “once-in-10,000-years rainfall event” because the word “event” is unnecessary. This also makes the whole sentence into the language of a chromedome, and bureaucratese, too. Acceptable substitutes include the following:
a) once-in-10,000-years rainfall
b) once-in-10,000-years rainstorm
c) once-in-10,000-years deluge
Here is a very recent example of the same kind of talking like a chromedome. A national retailer of automobiles has been advertising its “President’s Day sales event”.
The phrase “President’s Day Sale”, suffices very nicely.
Furthermore, “once-in-10,000-years” uses a suspiciously round number. It seems to have fallen out of a cloudless sky. It is very likely that this was really a once-in-8,888-years rainstorm or a once-in-12,345-years rainstorm, and it might have even been a once-in-202,220-years deluge.
More language of chromedomes: “We expect to complete the project within the next 5–10 years.” It should be written as it is said:
“We expect to complete the project within the next 5 to 10 years.”
“5-10 years” means either of these: “5 minus 10 years” (nonsense) or “5 through 10 years” (questionable).
The word “event” is one of those vague and sometimes meaningless words that are in the vogue. It is perfect for chromedomes. I have recently seen galleries of photos in which every one of them was labeled with words like these: “Lucy Lawless at an event for ‘Sparticus, Blood and Sand’,” or “Rita Hayworth at an event for ‘Blood and Sand’.”
“Event?” What kind of an event?
It is also true that during the 1940s, Ms. Hayworth was in a film called “Blood and Sand”. It was about bullfighting in Spain. I think that its title is most inappropriate for its time period because “Blood and Sand” makes me think of Tarawa, Eniwetok, Kwajalein, Saipan, Iwo Jima, and several other bloody, sandy islands in the Pacific.