Bone is the body part that forms the support structure of organism. There are several different types of skeleton: exoskeleton is the stable shell of organism, endoskeleton is the skeleton that forms the internal supporting structure of human body, hydroskeleton and cytoskeleton.

There are two main types of skeletons: solid and fluid. The solid skeleton can be internal (called internal skeleton) or external (called external skeleton), and can be further divided into flexible (elastic / movable) or rigid (hard / immovable). The fluid skeleton is always internal.

In western culture, skeleton is often regarded as a terrible symbol of death and supernatural phenomena. It's a popular theme for Halloween holidays and the day of the dead.