ABV stands for alcohol by volume and is defined as the percentage of ethanol (alcohol) present in 100 milliliters of liquid when said liquid is at a temperature of 68 degrees Fahrenheit. Today, it remains the standard means of measuring the amount of alcohol in any liquid, and is used worldwide.
ABV is different from “proof,” which is also regularly seen on spirits bottles in the United States. “Proof” is the ABV of a liquid multiplied by two. So, for example, a bourbon that is 90 proof would be 45 percent ABV.