From Longman Dictionary of Contemporary Englishfortyfor‧ty /ˈfɔːti $ ˈfɔːrti/ ●●● S3 W3 number 1 HMNthe number 402 → the forties3 → be in your forties4 → in the forties —fortieth adjective her fortieth birthdayOrigin forty Old English feowertig, from feower “four”