Adulthood is the state of being an adult. 成年
noun [抽象名词] 成年，成人时期
Few people nowadays are able to maintain friendships into adulthood. 现今很少有人能够把友谊维持到成年。
Few people nowadays are able to maintain friendships into adulthood. 现今很少有人能够把友谊维持到成年。