Idiopathic

Idiopathic means doctors don't know why something is happening. It's like when you have a puzzle and there is a piece missing, you don't know why it is missing or where it went, but it's not there. So, when doctors use the word "idiopathic," they mean they don't know why something is happening, like why you have a headache or a rash on your skin. They will try to figure it out, but sometimes the answer just isn't clear.