Regression means moving backward or returning to an earlier, often less developed state. When something regresses, it loses progress it had made.

In everyday life, you might see regression when a younger sibling who had been using the toilet independently starts having accidents again after a stressful event like starting school. Their behavior has regressed to an earlier stage. A student who was reading chapter books might regress to simpler books after being sick for weeks. An athlete recovering from an injury might regress in their performance before building back up to their previous level.

In mathematics, regression can describe when numbers approach a middle value over time. Very tall parents tend to have children who are taller than average, but shorter than them. That's called regression to the mean, where the extreme measurement moves back toward the average.

The opposite of regression is progression, moving forward or advancing. Think of regression as the rewind button: you're going back over ground you'd already covered, whether that's in learning, behavior, health, or development.