bifocals vs glasses

bifocals and glasses both are nouns.

Word	Noun	Adjective	Verb	Adverb
bifocals	Yes	No	No	No
glasses	Yes	No	No	No

As nouns, glasses is a hypernym of bifocals; that is, glasses is a word with a broader meaning than bifocals:

bifocals: (plural) eyeglasses having two focal lengths, one for near vision and the other for far vision
glasses: (plural) optical instrument consisting of a frame that holds a pair of lenses for correcting defective vision

Other hypernyms of bifocals include eyeglasses, specs, spectacles.

bifocals (noun)	glasses (noun)
(plural) eyeglasses having two focal lengths, one for near vision and the other for far vision	(plural) optical instrument consisting of a frame that holds a pair of lenses for correcting defective vision