NCI Dictionary of Cancer Terms
The NCI Dictionary of Cancer Terms features 7,916 terms related to cancer and medicine.
Browse the dictionary by selecting a letter of the alphabet or by entering a cancer-related word or phrase in the search box.
- listen (MY-kroh-OR-guh-NIH-zum)
- An organism that can be seen only through a microscope. Microorganisms include bacteria, protozoa, algae, and fungi. Although viruses are not considered living organisms, they are sometimes classified as microorganisms.