Believable means seeming true or real enough that people can accept it without much doubt. When a story is believable, the characters act like real people might act, and the events could actually happen. When someone gives a believable excuse for being late, you can imagine it really occurred that way.

The opposite is unbelievable, which describes something so far-fetched or unlikely that people can't accept it. If your friend claims they were late because aliens kidnapped them, that's not very believable. But if they say the bus broke down, that's easy to believe because it happens regularly.

In fiction, even fantasy stories need to be believable within their own rules. A wizard in a magical world feels believable because magic fits that setting. But if that same wizard suddenly started using a smartphone for no reason, it would break the believability.

People work hard to seem believable when they're acting in plays or movies. A believable performance means the actor makes you forget you're watching someone pretend. Similarly, when you write a story, making your characters' reactions believable helps readers stay engaged. If someone gets amazing news and just shrugs, that doesn't feel believable because most people would show more emotion.