A buddy is a friend or companion, especially someone you feel comfortable with and enjoy spending time around. When you pair up with a buddy for a field trip, you're choosing someone you trust to stick with you and help you stay on track. In swimming lessons, a buddy system means each person has a partner who watches out for them in the water.

The word carries a feeling of casual friendliness and equality. Your buddy might be a classmate who shares your lunch table, a teammate who practices with you after school, or a neighbor who joins you for bike rides. Unlike best friend, which suggests a deep, long-term bond, buddy can describe someone you simply get along with well.

People often use buddy as a friendly way to address someone directly: “Hey, buddy, want to play basketball?” Adults sometimes use it when talking to children they don't know well, like a coach greeting players before a game.

The phrase buddy up means to form a pair or partnership with someone. If a teacher says “buddy up for this activity,” you're choosing a partner to work alongside. Whether you're buddying up with someone for a science project or making a new buddy on the playground, the word suggests cooperation, companionship, and looking out for each other.