[noncount] :the act or process of removing unwanted substances from something :the act or process of making something pure

[noncount] :the act or process of improving something - often + of

[count] :an improved version of something - often + of

[count] :a small change that improves something

[noncount] :the quality of a person who has the good education, polite manners, etc., that are expected in people who belong to a high social class