Answer:
My first though water cures no thirst my next alone has soul and when he lives upon my first he then is called my whole.
The more of me there is the less you see.
What language does a billboard speak?
What is black when you buy it, red when you use it, and gray when you throw it away?
I have no voice but I can teach you all there is to know. I have spines and hinges but I am not a door. Once I’ve told you all I cannot tell you more.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.