noun, plural: microorganisms
Examples of microorganisms include bacteria, fungi, archaea, and protists. Viruses and prions, although microscopic, are not considered microorganisms by others because they are generally regarded as non-living.
Word origin: Gk: comb. form repr. mīkrós small + organism > organ: Gk órganon implement, tool, bodily organ.
Related forms: microorganic, microoganismal (adjective).