What Are Spirits?
Alcohol, in its basic meaning, is a hydroxyl compound such as ethanol or methanol. Fermentation is the process by which an organic substance (usually a sugar) is converted by a single-celled microorganism such as yeast into alcohol. A spirit is distilled alcohol. Spirits distillation is the process of heating a fermented liquid, evaporating off the alcohol as vapor, and thencondensing it back into liquid form.

How Are Spirits Measured?
Spirits are measured by alcohol content. Different scales are used in different countries. Most countries use alcohol by volume (ABV), also known as the Gay-Lussac system, which expresses alcohol content as a percentage of the total liquid volume of the beverage. A 40% ABV spirit contains 40% alcohol. In the United States, the proof scale of measurement is used, with the proof of a spirit being double the ABV. Thus a 40% ABV spirit is 80 proof. A degree symbol is customarily used when expressing proof.

How Are Spirits Classified?
Generally speaking, spirits are classified by the fermented material that they are distilled from. Whiskies, Vodka, Gin and most types of Schnapps are made by distilling a kind of beer made from grain. Brandy is made from fermented grape juice, and Fruit Brandy is made from other fruits. Rum and Cane Spirits derive from fermented sugar cane juice or molasses. Tequila and Mezcal come from the fermented pulp of the agave plant. Fortified wines are hybrid beverages in that they are a blend of fermented wine and distilled spirits (usually Brandy).