1. A circumscribed malformation of the skin, especially if colored by hyperpigmentation or increased vascularity.

A nevus may be predominantly epidermal, adnexal, melanocytic, vascular, or mesodermal, or a compound overgrowth of these tissues.

2. Any lesion containing melanocytes; any birthmark; mole.
3. A congenital discoloration of a circumscribed area of the skin as a result of pigmentation.
4. A circumscribed vascular tumor of the skin, usually congenital, due to hyperplasia of the blood vessels.
5. A benign pigmented spot on the skin; such as, a mole (a cluster of melanocytes and supportive tissue that appears as a tan, brown, or flesh-colored spot on the skin).
6. A benign blood vessel tumor on the skin; such as, a vascular nevus, a local collection of capillaries of the skin (a strawberry birthmark, stork mark, or port wine stain).
7. Etymology: from the Latin naevus meaning "a body mole"; especially, "a birthmark".