cnidarian vs scyphozoan

cnidarian and scyphozoan both are nouns.

Word	Noun	Adjective	Verb	Adverb
cnidarian	Yes	No	No	No
scyphozoan	Yes	No	No	No

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

cnidarian: radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms
scyphozoan: any of various usually free-swimming marine coelenterates having a gelatinous medusoid stage as the dominant phase of its life cycle

Other hyponyms of cnidarian include polyp, medusa, medusan, medusoid, jellyfish, hydroid, hydrozoan, actinozoan, anthozoan.

cnidarian (noun)	scyphozoan (noun)
radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms	any of various usually free-swimming marine coelenterates having a gelatinous medusoid stage as the dominant phase of its life cycle