Mythomoteur is a very big and fancy word that grown-ups use to describe something that happens in our brains. You know how sometimes you have really silly or goofy ideas that make no sense? Like imagining that your stuffed animals can talk or your toys have secret lives when you're not around. That's kind of like what mythomoteur is!
But it's not just about imagining silly things. Mythomoteur is also what happens when grown-ups believe in things that might not be true. Sometimes people can believe in stories or ideas so much that they start to act differently because of them. This can be a good thing if they believe in something like being kind to others or helping the environment. But it can be a bad thing if they believe in things that are mean or hurtful to others.
So, mythomoteur is like a big imagination that everyone has, but it's important to make sure we don't believe in things that hurt others or ourselves.