A falsehood is a statement that isn't true. When someone tells a falsehood, they're saying something that contradicts the facts, whether they know it or not. If your friend claims they saw a purple elephant in their backyard, that's a falsehood (unless they happen to live at a zoo with a very messy paint department).

Falsehoods come in different flavors. Some are innocent mistakes: you might spread a falsehood about when the library closes because you genuinely remembered the wrong time. Others are deliberate lies meant to deceive. A politician who knows the real numbers but claims otherwise is spreading a falsehood on purpose.

The word sounds formal because it often appears in serious contexts: newspapers correcting falsehoods in their reporting, scientists disproving falsehoods about how nature works, or historians identifying falsehoods in old accounts of events. You could simply say “lie” or “untruth,” but falsehood carries extra weight. It suggests something that matters, something worth correcting publicly and clearly.

The opposite of a falsehood is truth.