parallel bars vs bars

parallel bars and bars both are nouns.

Word	Noun	Adjective	Verb	Adverb
parallel bars	Yes	No	No	No
bars	Yes	No	No	No

As nouns, parallel bars and bars are synonyms defined as:

parallel bars and bars: gymnastic apparatus consisting of two parallel wooden rods supported on uprights

parallel bars (noun)	bars (noun)
gymnastic apparatus consisting of two parallel wooden rods supported on uprights	gymnastic apparatus consisting of two parallel wooden rods supported on uprights