coelenterate vs hydroid

coelenterate and hydroid both are nouns.

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

As nouns, hydroid is a hyponym of coelenterate; that is, hydroid is a word with a more specific, narrower meaning than coelenterate:

coelenterate: radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms
hydroid: colonial coelenterates having the polyp phase dominant

Other hyponyms of coelenterate include polyp, medusa, medusan, medusoid, jellyfish, scyphozoan, hydrozoan, actinozoan, anthozoan.

coelenterate (noun)	hydroid (noun)
radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms	colonial coelenterates having the polyp phase dominant