noun
adulthood; adult period
Refers to the stage of life after adolescence, typically from around age 20 onward in Japanese contexts.
成人期に入ると、責任が増える。
When you enter adulthood, your responsibilities increase.
彼は成人期のほとんどを海外で過ごした。
He spent most of his adult life abroad.
青年期 is adolescence or youth, the period before 成人期.
Compound of 成人 (adult) and 期 (period, stage).