Relapse means to fall back into a problem or bad situation after getting better or making progress. When someone recovers from an illness but then gets sick again, they have relapsed. When a student works hard to improve their grades but then stops studying and their grades drop again, that's a kind of relapse too.

The word comes up most often with health problems. A patient might recover from pneumonia, feel completely healthy for weeks, then relapse when the infection returns. Someone trying to break a bad habit, like biting their nails, might succeed for a month but then relapse under stress.

A relapse means sliding back significantly, returning to an earlier problematic state. If you're learning piano and play badly at one recital, that's a temporary struggle. But if you practice diligently for months, then completely stop practicing and forget what you learned, you've relapsed into your old non-practicing ways.

Understanding relapse helps us recognize that improvement isn't always a straight line upward. Sometimes progress includes stumbles backward, and recognizing a relapse can help you decide what to do next.

As a noun, a relapse is the return of the problem itself. As a verb, to relapse is to slide back into it.