sea anemone vs actinia

sea anemone and actinia both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea anemone	Yes	No	No	No
actinia	Yes	No	No	No

As nouns, actinia is a hyponym of sea anemone; that is, actinia is a word with a more specific, narrower meaning than sea anemone:

sea anemone: marine polyps that resemble flowers but have oral rings of tentacles; differ from corals in forming no hard skeleton
actinia: any sea anemone or related animal

Other hyponyms of sea anemone include actinian, actiniarian.

sea anemone (noun)	actinia (noun)
marine polyps that resemble flowers but have oral rings of tentacles; differ from corals in forming no hard skeleton	any sea anemone or related animal