In the past, a person usually moved from the status of child directly to the status of adult, often with this shift being marked by some type of coming-of-age test or ceremony.
After the social construct of adolescence was created, adulthood split into two forms: biological adulthood and social adulthood.
Depending on the context, adult can indicate either definition.
These criteria are social and subjective; they are organized by gender, race, ethnicity, social class, among other key identity markers.
As a result, particular populations feel adult earlier in the life course than do others.
Most modern societies determine legal adulthood based on reaching a legally specified age without requiring a demonstration of physical maturity or preparation for adulthood.
Historically and cross-culturally, adulthood has been determined primarily by the start of puberty (the appearance of secondary sex characteristics such as menstruation in women, ejaculation in men, and pubic hair in both sexes).