gill bar vs body structure

gill bar and body structure both are nouns.

Word	Noun	Adjective	Verb	Adverb
gill bar	Yes	No	No	No
body structure	Yes	No	No	No

As nouns, body structure is a hypernym of gill bar; that is, body structure is a word with a broader meaning than gill bar:

gill bar: one of the bony or cartilaginous arches on each side of the pharynx that support the gills of fishes and aquatic amphibians
body structure: a particular complex anatomical part of a living thing and its construction and arrangement

Other hypernyms of gill bar include anatomical structure, bodily structure, complex body part, structure.

gill bar (noun)	body structure (noun)
one of the bony or cartilaginous arches on each side of the pharynx that support the gills of fishes and aquatic amphibians	a particular complex anatomical part of a living thing and its construction and arrangement