Medium Riddles

What is black when you buy it, red when you use it, and gray when you throw it away?

What is cut on a table, but never eaten?

They come at night without being called and are lost in the day without being stolen. What are they?

I am taken from a mine, and shut in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

The more you take away, the larger I become. What am I?

What word is spelled incorrectly in every dictionary?

What can go up and down stairs without moving?

What gets bigger when more is taken away?

You saw me where I never was and where I could not be. And yet within that very place, my face you often see. What am I?

What 8-letter word has one letter in it?