improver vs add-on

improver and add-on both are nouns.

Word	Noun	Adjective	Verb	Adverb
improver	Yes	No	No	No
add-on	Yes	No	No	No

As nouns, improver and add-on are synonyms defined as:

improver and add-on: a component that is added to something to improve it

Other synonyms of improver include addition.

improver (noun)	add-on (noun)
a component that is added to something to improve it	a component that is added to something to improve it
someone devoted to the promotion of human welfare and to social reforms	a supplementary component that improves capability
	a software module that extends or enhances the capabilities of an existing application