(~s)
Frequency: The word is one of the 3000 most common words in English.
1.
If there is an ~ in something, it becomes better. If you make ~s to something, you make it better.
...the dramatic ~s in organ transplantation in recent years...
N-VAR
2.
If you say that something is an ~ on a previous thing or situation, you mean that it is better than that thing.
The new Prime Minister is an ~ on his predecessor...
N-COUNT: usu sing, oft N on n