A hairline refers to the edge of hair growth on the forehead, marking the boundary between the forehead and the hair. It can vary in shape and position among individuals, influenced by genetics, age, and hair loss patterns. Common types of hairlines include straight, widow's peak, and receding hairlines. Changes in a hairline can indicate various conditions, such as androgenetic alopecia, commonly known as male or female pattern baldness. Factors like stress, hormonal changes, and certain medical conditions can also affect hairline appearance. Maintaining a healthy lifestyle may help in preserving hair health and appearance.