A bone is one of the hard, strong pieces that form the skeleton inside your body. Your bones fit together like the frame of a building, giving your body its shape and protecting soft organs like your brain and heart. Without bones, you'd collapse into a puddle like a jellyfish on land.

You have 206 bones in your body, from the tiny stirrup bone in your ear (smaller than a grain of rice) to your femur, the long thigh bone that's the strongest bone you have. Bones aren't dead or unchanging: they're living tissue that grows as you grow, heals when broken, and constantly rebuilds itself throughout your life.

The word also appears in many expressions. When you feel something in your bones, you sense it deeply and instinctively. A bone of contention is something people argue about repeatedly. To bone up on a subject means to study it intensively, like boning up on your multiplication tables before a quiz. And when something is described as bare bones, it means stripped down to only the most essential parts, like a bare-bones camping trip with just a tent and sleeping bag.