sunglasses vs dark glasses

sunglasses and dark glasses both are nouns.

Word	Noun	Adjective	Verb	Adverb
sunglasses	Yes	No	No	No
dark glasses	Yes	No	No	No

As nouns, sunglasses and dark glasses are synonyms defined as:

sunglasses and dark glasses: (plural) spectacles that are darkened or polarized to protect the eyes from the glare of the sun

Other synonyms of sunglasses include shades.

sunglasses (noun)	dark glasses (noun)
(plural) spectacles that are darkened or polarized to protect the eyes from the glare of the sun	(plural) spectacles that are darkened or polarized to protect the eyes from the glare of the sun