To relearn something means to learn it again after you've forgotten it or after it has changed. When you relearn the multiplication tables you memorized in third grade but haven't used much since, you're rebuilding knowledge that faded from your memory. When a pianist who hasn't practiced in years sits down to relearn her favorite pieces, she's working to recover skills that grew rusty.

Sometimes we need to relearn things because the information itself has changed. A doctor who learned about treating diseases twenty years ago must relearn certain procedures as new research improves medical techniques. Someone who learned to type on a typewriter had to relearn typing when computers came along and introduced new keys and shortcuts.

Relearning is usually faster than learning something the first time. Your brain keeps traces of old knowledge even when you can't immediately recall it. It's like finding an old path through the woods: even if it's overgrown, you can still follow where it used to be. That's why athletes who return to a sport after years away, or students reviewing material from last year, often surprise themselves by how quickly it comes back.