adult是adolescere (grow up)的过去分词。

egg - embryo [胚胎] - foetus [就要出生的胎儿] - toddler [刚会走路] - adolescent (12~18) | teenager (13~19) - adult

Biologically [生物学], an adult is an organism that has reached sexual maturity. In human context, the term adult has meanings associated with social and legal concepts. In contrast to a "minor", a legal adult is a person who has attained the age of majority [成年的法定年龄] and is therefore regarded as independent, self-sufficient, and responsible. The typical age of attaining legal adulthood is 18, although definition may vary by legal rights, country, and psychological [心理的、精神的] development.

据说75 percent of people between the ages of 12 and 25 lack a clear sense of purpose and many young adults are intimidated by 'adulting.'

Contemporary adult education can take many different forms. Colleges and universities have instituted evening programs, extension work, courses without credit [学分], correspondence [通信] courses , distance learning programs (with courses transmitted to numerous locations), and online courses; community colleges have been especially active in this area.

Juvenile delinquency [青少年轻罪] is a legal term for behavior of children and adolescents that in adults would be judged criminal under law. In the United States, definitions and age limits of juveniles vary, the maximum age being set at 14 years in some states and as high as 21 years in others. The 16- to 20-year age group, considered adult in many places, has one of the highest incidences of serious crime.

When you come of age, you become legally an adult. If you are in your prime, you are at the stage when you are strongest, most active, or most successful.

近/反义词: full-grown grown-up mature; child, childish, childlike, immature

及冠(也称加冠、弱冠): 男子满二十岁之后，举行"及冠"之礼，表示已经是成年人了，可以取"字"。及笄(jī)之年的意思是古代女子满15岁，到了结婚的年龄。笄: 簪子。