A common mole is a growth on the skin that develops when pigment cells (melanocytes) grow in clusters. Most adults have between 10 and 40 common moles. These growths are usually found above the waist on areas exposed to the sun. They are seldom found on the scalp, breast, or buttocks.
Although common moles may be present at birth, they usually appear later in childhood. Most people continue to develop new moles until about age 40. In older people, common moles tend to fade away.
Another name for a mole is a nevus. The plural is nevi.