Body plan of an earthworm. Partitions (septa) divide the body cavity (coelom) into more than 100 …—© Merriam-Webster Inc.

Any member of a phylum (Annelida) of invertebrate animals that possess a body cavity (coelom), movable bristles (setae), and a body divided into segments by crosswise rings. Known as segmented worms, annelids are divided into three classes: marine worms (Polychaeta; see polychaete), earthworms (Oligochaeta), and leeches (Hirudinea).

This entry comes from Encyclopædia Britannica Concise.
For the full entry on annelid, visit

Seen & Heard

What made you look up annelid? Please tell us what you were reading, watching or discussing that led you here.