Nevus (plural: nevi) is the medical term for a mole. Nevi are very common. Most people have between 10 and 40. Common nevi are harmless collections of colored cells. They typically appear as small brown, tan, or pink spots.

You can be born with moles or develop them later. Moles that you’re born with are known as congenital moles. However, most moles develop during childhood and adolescence. This is known as an acquired nevus. Moles can also develop later in life as a result of sun exposure.

Nevi come in many shapes and sizes but most of them are harmless. Still, it’s important to keep an eye on your moles because changes could indicate a problem. If you’re worried about one or more of your moles, don’t hesitate to get it checked out by your plastic surgeon. He can do a biopsy to rule out skin cancer.