Any of a large group of single-celled, usually microscopic, eukaryotic organisms, such as amoebas, ciliates, flagellates, and sporozoans.

• 原生动物大批单细胞的，通常要在显微镜下才能看到的真核细胞有机体中的任何一种，包括变形虫、纤毛虫和孢子虫