Are units in English singular or plural?
Solution 1:
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.
Solution 2:
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.
Solution 3:
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.”
Solution 4:
In this case, as in many cases with the English language, one shouldn't try to use too much logic. There are things which I wouldn't touch with a ten-foot pole, and what kind of pole is that? One with a length of ten feet.
IIUC, this language particularity goes back rather far in the history of the English language, as it also exists in Dutch.