A boy is a young male human, usually a child or adolescent. When he becomes an adult, he is described as a man. The most apparent difference between a boy and 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.