Source : Webster's Revised Unabridged Dictionary (1913)

Twenty \Twen"ty\, n.; pl. {Twenties}.
   1. The number next following nineteen; the sum of twelve and
      eight, or twice ten; twenty units or objects; a score.

   2. A symbol representing twenty units, as 20, or xx.

Source : WordNet®

twenties
     n 1: the time of life between 20 and 30 [syn: {mid-twenties}]
     2: the decade from 1920 to 1929 [syn: {1920s}]