【Improve】 , 【better】 , 【help】 , 【ameliorate】 are comparable when denoting to mend or correct in part or in some degree.
【Improve】 , the general term, and 【better】 , more vigorous and homely, apply both to objects and to states or conditions that are not of necessity bad. With a reflexive pronoun 【improve】 implies a change for the 【better】 within oneself, 【better】 a change for the 【better】 in one′s social or financial status.
To 【help】 is to 【improve】 while still leaving something to be desired.
【Ameliorate】 is used chiefly in reference to conditions that are hard to bear or that cause suffering and implies partial relief or changes that make them tolerable.