The act of making something better or improving a situation. The amelioration of the city's public transportation system has significantly reduced commute times.
An improvement or enhancement in condition or quality. The new policies led to an amelioration in the working conditions for employees.
In historical linguistics, a semantic change in which a word develops a more favourable or positive meaning over time. The shift in meaning of 'knight' from 'servant' to 'mounted warrior' is a classic case of amelioration.