This familiar riddle describes something that can belong to you only while other people do not know it.
If you have one, you may feel tempted to tell somebody. But the moment you share it, it is no longer something known only to you.
Answer: A secret.
A secret fits every part of the clue. You can possess knowledge privately, want to share it with someone else, and lose its private status as soon as you reveal it. That contradiction is what makes this simple riddle so memorable.


