The prefix mis- means “badly,” “wrongly,” or “incorrectly.” When you add it to the beginning of a word, it changes the meaning to show that something was done in the wrong way or didn't turn out right.

If you understand something, you get it correctly. But if you misunderstand it, you've gotten it wrong, perhaps thinking your friend was angry when they were actually joking. When you spell a word correctly, you write it right, but when you misspell it, you've made an error. If you place your homework on your desk, you put it there intentionally, but if you misplace it, you've put it somewhere and now you can't find it.

You'll find this prefix in hundreds of common words: misbehave, miscalculate, mislead, mismatch, mistrust. Notice how the prefix always suggests something went wrong or wasn't quite right. Understanding this prefix helps you figure out the meaning of new words when you encounter them in your reading.