“成人期”常见的英文表达是 adulthood 。它指的是一个人达到法定成年年龄后所处的生命阶段，强调从生理、心理到社会角色等多方面已趋于成熟、独立的状态。
例句：
Adulthood brings with it a range of new responsibilities and opportunities.（成年期带来了一系列新的责任和机遇。）
During adulthood, people often focus on career development and family building.（在成年期，人们通常专注于职业发展和组建家庭。 ）