the.com/protozoan

means A single-celled organism (like an amoeba or paramecium) that behaves like a tiny animal — moving, feeding, and responding to its surroundings rather than photosynthesizing like a plant.

from From Greek protos, 'first,' plus zoion, 'animal' — coined in the 1800s by scientists carving up the newly-visible microscopic world, naming these creatures as the earliest, most primitive animal-like life forms. The same zoion root gives us 'zoo' and 'zodiac,' so protozoans are, etymologically, the original zoo exhibit.