improver vs annex

improver and annex both are nouns.

Word	Noun	Adjective	Verb	Adverb
improver	Yes	No	No	No
annex	Yes	No	Yes	No

As nouns, annex is a hyponym of improver; that is, annex is a word with a more specific, narrower meaning than improver:

Other hyponyms of improver include additive, afterthought, annexe, extension, wing, attachment, elongation, extension.

improver (noun)	annex (noun)
a component that is added to something to improve it	an addition that extends a main building
someone devoted to the promotion of human welfare and to social reforms

improver (verb)	annex (verb)
	add an extra part to
	take (territory) as if by conquest