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I am a little bit confused about using units in English, sometimes I hear that people use singular units for plural things, sometimes they use plural ones. Which one is correct?

  • 3 meter(s) long?
  • during a 2 week(s) period?
  • 0.5 dollar(s)
25

In Standard English, this crucially depends on whether the phrase is prenominal or not. Prenominally, the phrase will not show plural marking, while elsewhere it will have the normal plural marking, as appropriate.

Compare:

  • The bureau is 3 meters long.
  • This is a 3-meter-long bureau. (prenominal)


  • The period is 2 weeks.

  • This is a 2-week period. (prenominal)


  • The bill was 0.50 dollars.

  • This is a 0.50-dollar bill. (prenominal)

Note also that a hyphen is normally inserted to connect the words in the adjectival phrase when the phrase is prenominal.

  • Are you sure you should use plural even refering to less-than-one numbers? Wouldn't it be 0.50 dollar? – andrerpena Apr 22 '11 at 3:20
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    @Ciwee: Yes, I am sure. You should probably read this answer from another question. – Kosmonaut Apr 22 '11 at 12:16
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    The only time this doesn't hold true is if the stated quantity is 1. Only 1, if it's 1.00001 then it's plural again. The dresser is 1 meter long. It will take 1 week to get there. The bill was 1 dollar and some change. The bill was 1.15 dollars. The bill was one dollar and 15 cents. The bill was 1 dollar and 1 cent. Even plural with 0. The bill was 0 dollars and 86 cents. I have 0 apples and 1 orange. – Phoenix Nov 24 '11 at 9:09
7

See the NIST check list for a good concise reference about units in general. For hyphenated compound adjectives, which are in the singular: 3-meter long, a 2-week period. For the plural of noninteger quantities, the rule is that everything other than 1 uses the plural: 0.5 dollars.

1

It is common in informal spoken English, at least American, to omit the plural.

I got me a new fish pole, ten foot long!

Correct usage would be to say, "ten feet long."

  • 3
    Correct usage would be to say "I bough a new fish pole..." – Brian Carlton May 30 '12 at 18:39
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    @BrianCarlton bough, as in the noun bough? – Kent Munthe Caspersen Dec 28 '15 at 17:58
  • I’m not going to touch this one with a ten foot pole!     :-)    ⁠ – Scott Jun 26 '18 at 3:17
1

Simply put, units are inherently plural. For instance, the SI unit for time is seconds, the SI unit for mass is kilograms, and so forth. Therefore, when recording measurements, I think that it is acceptable to write “0.2 kilograms” and “0.95 seconds.” An equivalent expression for this example is “two-tenths of a kilogram” and “ninty-five-hundredths of a second.”

  • Your answer is good so far, but it doesn't address the second example. Why would one say "a two week period" instead of "a two weeks period"? – TaliesinMerlin Dec 26 '18 at 3:40

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