Cell

the smallest unit of living structure capable of independent existence, composed of a membrane-enclosed mass of protoplasm and containing a nucleus or nucleoid.

Description
Cells are highly variable and specialized in both structure and function, though all must at some stage replicate proteins and nucleic acids, utilize energy, and reproduce themselves. Other biomedical meanings include:
 * 1) a small closed or partly closed cavity; a compartment or hollow receptacle
 * 2) a container of glass, ceramic, or other solid material within which chemical reactions generating electricity take place