What is the meaning of tooth?

noun

• Hard bonelike structures in the jaws of vertebrates; used for biting and chewing or for attack and defense.
• Something resembling the tooth of an animal.
• Toothlike structure in invertebrates found in the mouth or alimentary canal or on a shell.
• A means of enforcement.
  • usage: "the treaty had no teeth in it"
• One of a number of uniform projections on a gear. .