Comparing "gaijin" and "gaishan"
改进 and 改善 both are verbs that mean to improve or to make something better and both are used in formal settings. Nonetheless, usually 改进 and 改善 cannot be used interchangeably as these words are used in very different contexts. 改进 is used to improve a method, technique, or work in a specific or tangible way, whereas 改善 is used to improve something that is more abstract an not easily measured, i.e., a quality of life, relations, an environment, etc.
