convex lens vs lens system

convex lens and lens system both are nouns.

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

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

convex lens: lens such that a beam of light passing through it is brought to a point or focus
lens system: a transparent optical device used to converge or diverge transmitted light and to form images

Other hypernyms of convex lens include lens, lense.

convex lens (noun)	lens system (noun)
lens such that a beam of light passing through it is brought to a point or focus	a transparent optical device used to converge or diverge transmitted light and to form images