the act of making something better; the process of something becoming better

a change in something that makes it better; something that is better than it was before

a significant/dramatic improvement

a slight/steady improvement

There has been a marked improvement in the quality of teaching.

The work should lead to an improvement in water quality.

The decade saw vast improvements in cardiology techniques.

We have made some mechanical improvements to the car.

This is a great improvement on your previous work.

The results are certainly an improvement over last year.

LEARNit Dictionary