Answer: It depends! +18 years old is considered a LEGALLY adult. Already Young can be said "physically young", you know?
Step-by-step explanation:
The minimum age to consider someone as an adult is 18 years old in many countries, including Brazil (My country hehe). This is due to a series of legal and social reasons, such as the ability to vote, to drive, to marry without authorization, to sign contracts, to be arrested as an adult, among others. The definition of "youth" varies according to the source, but generally includes people between 16 and 24 years old, since it is a phase of life with distinct characteristics and specific challenges.