To keep after someone means to persistently remind, encourage, or push them to do something they need to do. When your parents keep after you about practicing piano, they remind you again and again because they want you to improve. When a coach keeps after players about proper technique, she corrects them repeatedly until they get it right.

The phrase suggests steady, continuing pressure rather than a single reminder. A teacher might keep after a student who forgets to turn in homework, checking in day after day until it becomes a habit. It's not the same as nagging, which often feels annoying and pointless. When someone keeps after you, there's usually a good reason: they may see potential you're not using, or know you're capable of more than you're showing.

You can also keep after yourself, like when you make yourself practice basketball free throws every day even when you'd rather stop. Parents, teachers, and coaches keep after kids because certain skills and habits require repetition and persistence to develop. While it might feel tiresome in the moment, being kept after about important things can lead to real improvement.