From Latin 'adultus' — literally 'one who has finished growing,' the grammatical twin of 'adolescent.'
A person who is fully grown or has reached the age of legal majority.
From Latin adultus (grown up), the past participle of adolescere (to grow up), composed of ad- (toward) + alescere (to grow), the inchoative of alere (to nourish). The root PIE *h2el- (to grow, nourish) produced a wide family: Latin altus (high — "grown tall"), Latin alimentum (food), Latin alumnus (one who is nourished — a foster child), and Old Irish alim (I nourish). The relationship between "adult" and "adolescent
'Adult' and 'adolescent' are forms of the same Latin verb 'adolēscere' (to grow up). An 'adolescent' is someone who IS growing up (present participle 'adolēscēns'), while an 'adult' is someone who HAS grown up (past participle 'adultus'). The two words are grammatically a before-and-after pair from a single verb. Despite the similar