optical lens vs lens system

optical lens and lens system both are nouns.

Word	Noun	Adjective	Verb	Adverb
optical lens	Yes	No	No	No
lens system	Yes	No	No	No

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

optical lens: a lens that focuses the image in a camera
lens system: a transparent optical device used to converge or diverge transmitted light and to form images

Other hypernyms of optical lens include lens, lense.

optical lens (noun)	lens system (noun)
a lens that focuses the image in a camera	a transparent optical device used to converge or diverge transmitted light and to form images