A Prophecy
Something that tells you what's going to happen. Usually by some magical creature or a wizard with a bad attitude.
'The prophecy says I'm gonna fail my math test. I believe it.', @MathHater4Life
My grandma told me a prophecy. It was about my future and it was completely wrong. Also, it was about her cat.
My mom said the prophecy told her I'd marry a guy named Dave. I just married Dave. She was right.