Re is a prefix meaning “again” or “back.” When you reread a chapter in a book, you read it again. When you return a library book, you bring it back. When you rebuild a sandcastle after a wave destroys it, you build it again from scratch.

This little prefix appears in hundreds of English words. You might rethink a decision, meaning you think about it again with fresh eyes. A teacher might ask you to rewrite a messy paragraph. When you review your notes before a test, you're looking at them again. When something recurs, it happens again and again.

Sometimes re- suggests doing something better the second time around, like when you revise an essay to improve it. Other times it just means repetition, like when you replay your favorite song.

Notice how re- works: it attaches to the front of action words to create new meanings. Do becomes redo. Start becomes restart. Consider becomes reconsider. Once you recognize this pattern, you'll spot it everywhere and understand new words instantly, even if you've never seen them before.