Incisor

Incisors (from Latin incidere, "to cut") are the front teeth present in most heterodont mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, whereas armadillos have none.[1]

Incisors are most remarkable in rodents in which their incisors constantly grow throughout their lives and must be worn down by gnawing.