shellfish vs huitre

shellfish and huitre both are nouns.

Word	Noun	Adjective	Verb	Adverb
shellfish	Yes	No	No	No
huitre	Yes	No	No	No

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

shellfish: meat of edible aquatic invertebrate with a shell (especially a mollusk or crustacean)
huitre: edible body of any of numerous oysters

shellfish (noun)	huitre (noun)
invertebrate having a soft unsegmented body usually enclosed in a shell	edible body of any of numerous oysters
meat of edible aquatic invertebrate with a shell (especially a mollusk or crustacean)