cnidaria

As nouns the difference between sponge and cnidaria

is that sponge is (countable) any of various marine invertebrates, mostly of the phylum porifera , that have a porous skeleton often of silica while cnidaria is cnidarian.

As a verb sponge

is (slang) to take advantage of the kindness of others.

As nouns the difference between metazoan and cnidaria

is that metazoan is (zoology) any animal that undergoes development from an embryo stage with three tissue layers, namely the ectoderm, mesoderm, and endoderm the term applies to all animals except the sponges while cnidaria is cnidarian.

As an adjective metazoan

is having to do with animals that develop from an embryo with three tissue layers.