WordNet sense 1 (a highly developed state of perfection; having a flawless or impeccable quality):

cultivation, culture, finish, polish, polish

WordNet sense 2 (the process of removing impurities (as from oil or metals or sugar etc.)):

purification, refining

WordNet sense 3 (the result of improving something):

elaboration

WordNet sense 4 (a subtle difference in meaning or opinion or attitude):

nicety, nuance, shade, subtlety

WordNet sense 5 (the quality of excellence in thought and manners and taste):

civilization, civilisation