To lie means to say something you know isn't true in order to deceive someone. When you lie, you're not making an honest mistake or misremembering something: you're deliberately telling a falsehood because you want someone to believe something that isn't real.

A student who lies about finishing their homework knows they didn't do it but says they did. Someone who lies about breaking a vase might blame the family dog, even though they saw exactly what happened. People lie for different reasons: to avoid getting in trouble, to make themselves look better, to protect someone's feelings, or sometimes just out of habit.

Lying damages trust. When you lie to your friends, parents, or teachers, they start wondering what else you might be dishonest about. Once someone catches you in a lie, they may question everything you say, even when you're telling the truth.

Some people talk about small social kindnesses, like telling your aunt you love her thoughtful gift even when you don't, as being in a gray area that they don't consider real lies. But deliberate deception about important things, especially to escape consequences or harm others, causes real harm.

A liar is someone who lies, and a lie (as a noun) is the false statement itself.