FIFTIES

[plural] [noun]The fifties is the range of temperature between 50° and 59°.It's been in the fifties all week.The fifties is also the period of years between 50 and 59 in any century.Rock and roll first became popular in the fifties (= between 1950 and 1959).A person's fifties are the period in which they are aged between 50 and 59.My dad is in his fifties.