Incisor

Incisors (from Latin incidere, "to cut") are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.

In many herbivorous or omnivorous mammals, such as the human and the horse, they are adapted for shearing sharply. In cats, the incisors are small and do not do much; biting off meat is done with the canines and the carnassials. In elephants, the upper incisors are modified into curved tusks, just as is the case with Narwhals, where normally one of them develops into a straight and twisted tusk. The incisors of rodents grow throughout life and are worn by gnawing.

Humans normally have eight (8) incisors, two of each type. The types of incisors are:

• maxillary central incisor
• maxillary lateral incisor
• mandibular central incisor
• mandibular lateral incisor

Among other animals, some other primates, cats and horses have twelve. The rodents have four. Rabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having eight--1 small pair, called "peg teeth" is directly behind the most anterior pair.