Teeth are the hard, white structures in your mouth that you use to bite and chew food. Each tooth is incredibly strong, covered with enamel (the hardest substance in your body), but also alive, with nerves and blood vessels inside.

Humans get two sets of teeth in their lifetime. Your first set, called baby teeth or primary teeth, starts falling out around age six. These are gradually replaced by permanent teeth, which need to last the rest of your life. Adults typically have 32 teeth, including molars for grinding, sharp canines for tearing, and incisors for biting.

Different animals have teeth shaped for their diets. Sharks grow new teeth throughout their lives (some go through 30,000 teeth!). Herbivores like horses have flat teeth perfect for grinding grass. Carnivores like lions have sharp, pointed teeth for tearing meat.

The phrase “by the skin of your teeth” means barely escaping something or succeeding by the thinnest margin. When someone grits their teeth, they clench their jaw, usually while enduring something difficult or painful. And if something has teeth, like a law or rule, it means it has real power to enforce consequences.