Liquor refers to a distilled alcoholic beverage, such as vodka, whiskey or brandy. Distilled liquor (pronounced something like LIK-er) is very high in alcoholic content (sometimes as high as forty-percent alcohol per volume, or eighty-proof) and can rapidly cause drunkeness.
Distilled liquor was uncommon in the early medieval period, but became increasingly common toward the end. It was discovered by Muslim scholars in the 8th Century, and made its way to Europe by the 10th Century, but was widely used more as a medicine than as a recreational beverage. Examples of this include brandy, aqua vitae and whiskey, but by the end of the medival era most modern types of distilled liquor were distinctly recognizable in their modern forms.
Distilling most kinds of liquor involves fermenting a mash of grains such as barley or rye (or fruits, berries or even potatoes]), into an alcoholic mix then heating the mash in special vessels. This evaporates the alcohol, which is then cooled and collected, typically in an assembly of coiled copper tubing. Local variations in the ingredients of the mash, the specific details of the distillation process, and even the heat source create the wide variety of distilled liquors available. Scotch whiskey, Irish whiskey and Rye whiskey are all types of whiskey, for example, but have distinct flavours and subtle differences in colour which stem from the differences in their ingredients and distillation. In addition, many commercially available liquors are aged, allowed to sit for years or even decades, to mellow and enrich their flavour.