1. The smallest unit of living structure capable of independent existence, composed of a membrane-enclosed mass of protoplasm and containing a nucleus or nucleoid. Cells are highly variable and specialized in both structure and function, although all must at some stage replicate proteins and nucleic acids, use energy, and reproduce themselves. 2. A small closed or partly closed cavity; a compartment or hollow receptacle. 3. A container of glass, ceramic, or other solid material within which chemical reactions generating electricity take place or solutions are placed for photometric assays. [L. cella, a storeroom, a chamber]
1. any of the protoplasmic masses making up organized tissue, consisting of a nucleus surrounded by cytoplasm enclosed in a cell or plasma membrane. It is the fundamental, structural, and functional unit of living organisms. In some of the lower forms of life, such as bacteria, a morphological nucleus is absent, although nucleoproteins (and genes) are present.