Wouldn't is the shortened form of “would not.” It's used to talk about things someone refuses to do, things that didn't happen in the past, or things that won't happen under certain conditions.

You might say “I wouldn't eat that” to mean you refuse to eat something, or “The door wouldn't open” to describe a door that refused to budge no matter how hard you pushed. When you say “She wouldn't listen,” you mean she refused to pay attention.

The word also appears in conditional statements about imaginary situations: “I wouldn't want to be lost in the woods” means that if you were in that situation, you wouldn't like it. Or “He wouldn't hurt a fly” describes someone so gentle they'd never harm anything.

Sometimes wouldn't expresses typical behavior: “My cat wouldn't come when I called” suggests this is normal for your cat. The word can also show polite offers: “Wouldn't you like some lemonade?” sounds friendlier than “Do you want lemonade?”

The opposite of wouldn't is would: “I would help” versus “I wouldn't help.” Using contractions like wouldn't makes speech and writing sound more natural and conversational.