loon vs gaviiform seabird

loon and gaviiform seabird both are nouns.

Word	Noun	Adjective	Verb	Adverb
loon	Yes	No	No	No
gaviiform seabird	Yes	No	No	No

As nouns, gaviiform seabird is a hypernym of loon; that is, gaviiform seabird is a word with a broader meaning than loon:

loon: large somewhat primitive fish-eating diving bird of the Northern Hemisphere having webbed feet placed far back; related to the grebes
gaviiform seabird: seabirds of the order Gaviiformes

loon (noun)	gaviiform seabird (noun)
large somewhat primitive fish-eating diving bird of the Northern Hemisphere having webbed feet placed far back; related to the grebes	seabirds of the order Gaviiformes
a worthless lazy fellow
a person with confused ideas; incapable of serious thought