A mandible is the lower jaw bone in humans and other vertebrates, the bone that holds your bottom teeth and moves when you open your mouth to eat, talk, or yawn. While your upper jaw stays fixed to your skull, your mandible is the only bone in your head that can move freely, acting like a hinged door that swings down and up.

The mandible is one of the strongest bones in your body, designed to withstand the powerful forces of chewing. When you bite into a crunchy apple or chew tough meat, your jaw muscles pull on your mandible, creating enough pressure to break down food. In humans, the mandible is a horseshoe-shaped bone that you can feel along your jawline from your chin to the area just below your ears.

Scientists and doctors often use the word mandible instead of “lower jaw,” especially when discussing anatomy or examining fossils. Paleontologists might discover an ancient human mandible at an archaeological site, learning about diet and health from the teeth still attached to it.

Insects also have mandibles, though theirs work differently: an ant's mandibles are like pincers that move side to side rather than up and down, perfect for carrying food or defending the colony.