A boy is a young male human, usually child or adolescent. When he becomes an adult he's described as a man. The most apparent thing that differentiates a boy from a girl is that a boy typically has a penis while girls have a vagina. However, some intersex children with ambiguous genitals, and genetically female transgender children may also be classified or self-identify as a boy.The term "boy" is primarily used to indicate biological sex distinctions, cultural gender role distinctions or both. The latter most commonly applies to adult men, either considered in some way immature or inferior, in a position associated with aspects of boyhood, or even without such boyish connotation as age-indiscriminate synonym. The term can be joined with a variety of other words to form these gender-related labels as compound words.