attachment vs improver

attachment and improver both are nouns.

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

As nouns, improver is a hypernym of attachment; that is, improver is a word with a broader meaning than attachment:

Other hypernyms of attachment include add-on, addition.

attachment (noun)	improver (noun)
the act of fastening things together	a component that is added to something to improve it
the act of attaching or affixing something	someone devoted to the promotion of human welfare and to social reforms
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