A sarcophagus is a stone container for a coffin or body. The word comes from Greek "sarx" meaning to eat, and "Phagos" meaning flesh, so sarkophagos (σαρκοφαγος), which means "eater of flesh". Herodotus believed, erroneously, that sarcophagi (the Latin plural) were carved from a special kind of rock that consumed the flesh of the corpse inside.
Sarcophagi were usually carved, decorated or built ornately. Some were built to be freestanding above ground, as a part of an elaborate tomb. Others were made for burial, or were placed in crypts. A sarcophagus was usually the external layer of protection for a royal Egyptian mummy, with several layers of coffins nested within.
The word sarcophagus is often used in context of the Chernobyl nuclear disaster, to describe a concrete tomb structure that has been erected to isolate the remains of the collapsed atomic reactor from the environment.