Simple Definition:

A fable is a short story that teaches a moral lesson [a lesson about how to behave or what is right and wrong]. It often features animals that can talk or act like humans. For example, in the fable “The Tortoise and the Hare,” the slow-moving tortoise teaches the lesson that perseverance [not giving up] is more important than speed.

Very Simple Definition:

A fable is a short story that teaches a lesson. It usually has talking animals. In the story “The Tortoise and the Hare,” the slow tortoise teaches us that it’s important to keep trying.