noun
one's 20s; twenties
Refers to the age range 20–29 or people in that age group. Often used with possessive or descriptive phrases.
彼は二十代で起業した。
He started his business in his twenties.
この調査は二十代の女性を対象にしている。
This survey targets women in their twenties.
Compound of 二十 (twenty) and 代 (generation, era, range), literally 'the twenty range'.