A brother is a boy or man who shares one or both parents with you. If you and another person have the same mother and father, you're full brothers. If you share just one parent, you're half brothers. Brothers grow up together in the same family, which often creates a unique bond, sometimes close and supportive, sometimes competitive and challenging, usually both.

The relationship between brothers can be complicated. One day you might be best friends playing basketball in the driveway, the next day arguing over whose turn it is to take out the trash. Many brothers tease each other mercilessly but defend each other fiercely when someone outside the family causes trouble. As brothers grow up together, they share countless experiences: family vacations, holiday traditions, and inside jokes that no one else understands.

The word also extends beyond biological family. People sometimes call close male friends their brothers, especially when that friendship feels as strong and loyal as a family bond. Members of fraternities call each other brothers. Religious communities, like monks or priests, often refer to each other as brothers. In these cases, the word captures that sense of deep connection, shared experience, and mutual support that characterizes the best of brotherhood.