What does Proof and percent alcohol mean?

When you are wanting to know what the percent alcohol is, in your liquor, it is a pretty simple thing to figure out. If the bottle says 100 proof that means it is 50 percent alcohol. If the bottle says it is 82 proof that would make it 41 percent alcohol.  So basically the alcohol content is half of whatever the proof is. The higher the proof the more alcohol it contains. 40 proof would mean it is only 20 percent alcohol. This rule applies to any kind of alcohol that you can drink. If you have a bottle of wine that says it is 20 proof it would only be 10 percent alcohol.