An order of minute worms which usually have one or two groups of vibrating cilia on the head, which, when in motion, often give an appearance of rapidly revolving wheels. The species are very numerous in fresh waters, and are very diversified in form and habits.

Phylum of microscopic, transparent animals distinguished by rings of cilia around the anterior end, which cause the appearance of whirling. Rotifers are abundant in the plankton community and are important for nutrient recycling in aquatic systems.

a phylum including: rotifers