A boy is a male child or young person, typically from birth through the teenage years. When someone refers to a boy, they usually mean someone younger than about 18, though the exact age range can vary. A group of boys might be playing basketball at recess, building a fort in the backyard, or working together on a science project.

The word appears in many common phrases and expressions. A Boy Scout is a member of a youth organization that teaches outdoor skills and leadership. Someone might say “boys will be boys” when kids are being rowdy or energetic, though this phrase can sometimes excuse behavior that shouldn't be excused. When parents talk about their boy, they mean their son, no matter how old he gets.

In older times, the word was sometimes used disrespectfully toward adult men, particularly in contexts of discrimination. Today, using boy to address an adult man is considered inappropriate and offensive.

The word can also express surprise or emphasis, as in “oh boy!” when something exciting or challenging is about to happen. A boyish quality means having characteristics associated with youth, like enthusiasm or playfulness.