improver vs attachment

improver and attachment both are nouns.

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

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

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

improver (noun)	attachment (noun)
a component that is added to something to improve it	the act of fastening things together
someone devoted to the promotion of human welfare and to social reforms	the act of attaching or affixing something
	faithful support for a cause or political party or religion
	a supplementary part or accessory
	a connection that fastens things together
	a writ authorizing the seizure of property that may be needed for the payment of a judgment in a judicial proceeding
	a feeling of affection for a person or an institution