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Nouns with decimals


Should I use a singular or plural noun with decimals below 1? Is it correct to write 0.5 hour? Or, is it 0.5 hours?


In Practical English Usage (1995), Michael Swan tells us that singular nouns are generally used with decimals (and fractions) below 1. For example:

  • 0.5 hour (or one half hour)
  • 0.1625 cm (or zero point one six two five of a centimetre)

Decimals (and fractions) over 1 are followed directly by a plural noun, as in the following examples:

  • 1.5 hours (or one and one half hours)
  • 1.3 millimetres (or one point three millimetres)