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improve (up)on something
to make something better. (Upon is formal and less commonly used than on.) Do you really think you can improve upon this song? No one can improve on my favorite melody.
Make beneficial additions or changes to, as in The company is trying to improve on the previous model. [Late 1600s]
improve onor improve upon
To make beneficial additions or changes to something; make something better: We can improve on this room by painting it. I improved upon the recipe by adding more spices.