hydroid vs siphonophore

hydroid and siphonophore both are nouns.

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

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

hydroid: colonial coelenterates having the polyp phase dominant
siphonophore: a floating or swimming oceanic colony of polyps often transparent or showily colored

Other hyponyms of hydroid include planula, hydra, sertularian.

hydroid (noun)	siphonophore (noun)
colonial coelenterates having the polyp phase dominant	a floating or swimming oceanic colony of polyps often transparent or showily colored