gill bar vs gill arch

gill bar and gill arch both are nouns.

Word	Noun	Adjective	Verb	Adverb
gill bar	Yes	No	No	No
gill arch	Yes	No	No	No

As nouns, gill bar and gill arch are synonyms defined as:

gill bar and gill arch: one of the bony or cartilaginous arches on each side of the pharynx that support the gills of fishes and aquatic amphibians

Other synonyms of gill bar include branchial arch.

gill bar (noun)	gill arch (noun)
one of the bony or cartilaginous arches on each side of the pharynx that support the gills of fishes and aquatic amphibians	one of the bony or cartilaginous arches on each side of the pharynx that support the gills of fishes and aquatic amphibians