The maxilla is the upper jaw bone in your skull. While your lower jaw (called the mandible) moves up and down when you talk or chew, your maxilla stays fixed in place as part of your skull.

Your maxilla holds your top teeth and forms several important structures in your face: the roof of your mouth, part of your eye sockets, and the sides of your nose. When you run your tongue along the hard, bony roof of your mouth, you're feeling the bottom surface of your maxilla.

You actually have two maxillary bones, one on each side of your face, that fuse together before you're born. Dentists and doctors pay close attention to the maxilla because it affects how your teeth line up, how your face develops as you grow, and even how you breathe. When orthodontists talk about expanding a child's maxilla, they mean gradually widening the upper jaw to create more space for teeth or to improve breathing.

Scientists use maxillary as an adjective to describe things related to the upper jaw, like your maxillary teeth (the ones in your upper jaw) or your maxillary sinuses (air-filled spaces in the bone that can get stuffed up when you have a cold).