Nevus (or naevus, plural nevi, from nævus, latin for birthmark) is the meical term for sharply-circumscribed and chronic lesions of the skin. These lesions are commonly named birthmarks and moles. By definition, nevi are benign. Histologically, nevi are differentiated from lentigos (also a type of benign pigmented macule) by the presence of nests of melanocytes, which lentigines (pl. form of lentigo) lack.