Alopecia is a medical condition characterized by hair loss from the scalp or other parts of the body. It can occur in various forms, ranging from small, round patches of hair loss (alopecia areata) to complete hair loss on the scalp (alopecia totalis) or the entire body (alopecia universalis). It can be temporary or permanent. Alopecia may be caused by genetic factors, autoimmune disorders, hormonal imbalances, or other underlying medical conditions.