micro organism
/ˌmaɪkroʊˈɔːrɡənɪzəm/
noun
- A very small living thing that can only be seen with a microscope; includes bacteria, viruses, and some fungi.
- Yogurt contains beneficial micro-organisms that help with digestion.
- Scientists study micro-organisms to understand how diseases spread.
- The pond water was full of tiny micro-organisms visible under a microscope.