Nematoda vs. Annelida

Nematoda

A phylum of worms, having a long, round, and generally smooth body; the roundworms. They are mostly parasites, in plants and animals, but some are free-living in soil or water. Also called Nematoidea.

Nematodanoun

unsegmented worms: roundworms; threadworms; eelworms

Annelida

A division of the Articulata, having the body formed of numerous rings or annular segments, and without jointed legs. The principal subdivisions are the Chætopoda, including the Oligochæta or earthworms and Polychæta or marine worms; and the Hirudinea or leeches. See Chætopoda.

Annelidanoun

segmented worms: earthworms; lugworms; leeches