Underarm 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 underarm hair can vary widely among individuals and cultures. Some people choose to remove it for aesthetic or hygiene reasons, while others prefer to keep it. The choice often reflects personal preferences, societal norms, or cultural practices related to body hair, such as those seen in Western culture or Eastern culture.