Armpit hair, also known as axillary hair, is the hair that grows in the underarm area of the human body. It typically begins to develop during puberty due to hormonal changes, particularly the increase in androgens. This hair serves several functions, including reducing friction during arm movement and providing a surface for the secretion of sweat and pheromones. The presence and grooming of armpit hair vary across cultures and individuals. Some people choose to remove it for aesthetic or hygiene reasons, while others prefer to keep it. The decision often reflects personal preferences, cultural norms, and societal influences regarding body hair.