1. (n.) The number four; a collection of four things; a quaternion.
2. (n.) A tetravalent or quadrivalent atom or radical; as, carbon is a tetrad.
Thesaurus Entries
Euglena, adenovirus, aerobe, aerobic bacteria, amoeba, anaerobe, anaerobic bacteria, animalcule, bacillus, bacteria, bacterium, bug, coccus, colon bacillus, diatom, disease-producing microorganism, dyad, echovirus, enterovirus, filterable virus, flagellate, fungus, germ, gram-negative bacteria, gram-positive bacteria, microbe, microorganism, microspore, microzoa, mold, monad, nematode, nonfilterable virus, paramecium, pathogen, picornavirus, protozoa, protozoon, reovirus, rhinovirus, rickettsia, salmonella, saprophyte, spirillum, spirochete, spore, sporozoon, staphylococcus, streptococcus, tetrad, triad, trypanosome, vibrio, virus, volvox, vorticellum, zoospore
