uneven bars vs bars

uneven bars and bars both are nouns.

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

As nouns, bars is a hypernym of uneven bars; that is, bars is a word with a broader meaning than uneven bars:

uneven bars: a pair of parallel bars set at different heights; used in women's gymnastics
bars: gymnastic apparatus consisting of two parallel wooden rods supported on uprights

Other hypernyms of uneven bars include parallel bars.

uneven bars (noun)	bars (noun)
a pair of parallel bars set at different heights; used in women's gymnastics	gymnastic apparatus consisting of two parallel wooden rods supported on uprights