Shell

Amongst other things, a shell is:

• An animal shell, the hard, rigid outer covering of an animal such as a mollusk or gastropod. See also: shell (material).
• An operating system shell, such as a UNIX shell command line interpreter in the Unix operating system.
• An electron shell (energy level), consisting of a number of electrons in an orbital around an atomic nucleus
• The shorthand name for Shell Oil's line of convenience stores.
• A projectile with explosive charge, shot from a gun; typically shells are larger than bullets and shot from larger guns. See shell (projectile).
• In physics, see On shell and Off shell
• shell (fruit)
• turtle shell