FORTIES

[plural] [noun]The forties is the range of temperature between 40° and 49°.The temperature is expected to be in the forties tomorrow.The forties is also the period of years between 40 and 49 in any century.Our house was built some time in the forties (= between 1940 and 1949).A person's forties are the period in which they are aged between 40 and 49.I'd never have known she was in her forties - she looks so young.