ETYM Akin to nock; cf. od. nock, OSw. nocka. Related to Nick a notch.
(Irregular plural: notches).
1. A V-shaped indentation.
2. A small cut; SYN. nick, snick.

Round tooth or teeth.

ETYM Etymology uncertain.
1. Has teeth on the rims to pull film or paper through.
2. Thin wheel with teeth that engage with a chain; SYN. sprocket wheel.

ETYM Old Eng. toth,tooth, as. tôth.
(Irregular plural: teeth).
1. Hard bonelike structures in the jaws of vertebrates; used for biting and chewing or for attack and defense.
2. Toothlike structure in invertebrates found in the mouth or alimentary canal or on a shell.
3. Something resembling the tooth of an animal.
In vertebrates, one of a set of hard, bonelike structures in the mouth, used for biting and chewing food, and in defense and aggression. In humans, the first set (20 milk teeth) appear from age six months to two and a half years. The permanent dentition replaces these from the sixth year onward, the wisdom teeth (third molars) sometimes not appearing until the age of 25 or 30. Adults have 32 teeth: two incisors, one canine (eye tooth), two premolars, and three molars on each side of each jaw. Each tooth consists of an enamel coat (hardened calcium deposits), dentine (a thick, bonelike layer), and an inner pulp cavity, housing nerves and blood vessels. Mammalian teeth have roots surrounded by cementum, which fuses them into their sockets in the jawbones.
The neck of the tooth is covered by the gum, while the enamel-covered crown protrudes above the gum line.
The chief diseases of teeth are misplacements resulting from defect or disturbance of the tooth-germs before birth, eruption out of their proper places, and caries (decay).
A genetically engineered protein able to stimulate the recovery of tooth tissue in decayed teeth was undergoing trials 1993. + prikaži više