improver
1. [ noun ] someone devoted to the promotion of human welfare and to social reforms
Synonyms: do-gooder humanitarian
Related terms: benefactor better
2. [ noun ] a component that is added to something to improve it
Synonyms: addition add-on
Examples:

"the addition of a bathroom was a major improvement" "the addition of cinammon improved the flavor"

Related terms: component additive attachment afterthought elongation softener annex better
Similar spelling:   improve
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  improper
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  improvise
  improvable
  improperly
  improvement
  improving
  imbrue
  improvised
  improvident
  impropriety
  improbable
  imprint
  impress