The word proof can mean:

• originally, a test assessing the validity or quality of something.

• a rigorous, compelling argument, including:
  • a logical argument or a mathematical proof (see also proof theory).
  • a legal proof .
  • a large accumulation of scientific evidence.

• a photograph, print or page layout presented as an example for proofreading or approval.

• alcoholic proof, a measure of how much ethanol is in an alcoholic beverage.

• proof coinage, a coin made as an example of a particular strike.

• Proof (play), a play by David Auburn.

• Proof (movie) , a film by Jocelyn Moorhouse .

• Proof (rapper), a rapper and member of the group D12.

• Yeast (baking) yeast or leavening agent, with sugar and water before making activator, beer, bread, cider, dough, or wine.