Microorganism — Science definition
Any organism too small to see unaided; a category of size, not of harm, and most are harmless or useful.
Where it is taught
- Microorganisms, Barriers & Immune Defense — Coordination, Defense & Reproduction, Life Science & Scientific Inquiry, Grade 7
In use
A microorganism is any organism too small to see without a microscope — bacteria, many fungi, single-celled protists.
Microorganisms, Barriers & Immune Defense