To reach an age, 18 or 21 years, for example, at which one is no longer eligible for certain special services, such as education or protection, from the state.
法定年齡：到達(dá)一定年齡，例如18歲或21歲，不再享受國(guó)家的諸如教育或保護(hù)的某些特殊照顧
[usa. in imperative]behave in a manner appropriate to someone of one's age and not to someone much younger
行為與年齡相稱
(of a person) reach adult status (in UK law at 18, formerly 21)
（人）成年（英國(guó)法律現(xiàn)規(guī)定18歲成年，原為21歲）
old enough to be able or expected to do something
到了…的年齡
the sons are of an age to marry.
兒子們到了結(jié)婚的年齡。
(of two or more people or things) of a similar age
（兩者，多人，多物）年齡近似的
the children all seemed of an age.
孩子們看起來差不多大。