microorganism

(mī″krō-or′gă-nĭzm)

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[micro- + organism]
A living organism too small to be seen with the naked eye, esp. a virus, bacterium, fungus, protozoan, or intracellular parasite, and some helminths. Many specialists do not consider viruses to be microorganisms because viruses are not cellular and cannot replicate without a host cell.
SEE: germ; SEE: microbe

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