sunglass vs convex lens

sunglass and convex lens both are nouns.

Word	Noun	Adjective	Verb	Adverb
sunglass	Yes	No	No	No
convex lens	Yes	No	No	No

As nouns, convex lens is a hypernym of sunglass; that is, convex lens is a word with a broader meaning than sunglass:

sunglass: a convex lens that focuses the rays of the sun; used to start a fire
convex lens: lens such that a beam of light passing through it is brought to a point or focus

Other hypernyms of sunglass include converging lens.

sunglass (noun)	convex lens (noun)
a convex lens that focuses the rays of the sun; used to start a fire	lens such that a beam of light passing through it is brought to a point or focus