hydrozoan vs hydroid

hydrozoan and hydroid both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydrozoan	Yes	No	No	No
hydroid	Yes	No	No	No

As nouns, hydrozoan and hydroid are synonyms defined as:

hydrozoan and hydroid: colonial coelenterates having the polyp phase dominant

hydrozoan (noun)	hydroid (noun)
colonial coelenterates having the polyp phase dominant	colonial coelenterates having the polyp phase dominant