Whisky or whiskey is a type of liquor made from fermented grain mash. Various grains are used for different varieties, including barley, corn, rye, and wheat. Whisky is typically aged in wooden casks, which are typically made of charred white oak. Uncharred white oak casks previously used for the aging of port, rum or sherry are also sometimes used.

Liquor is an alcoholic drink produced by the distillation of grains, fruits, vegetables, or sugar that have already gone through alcoholic fermentation. Other terms for liquor include: spirit, distilled beverage, booze, spirituous liquor or hard liquor. The distillation process concentrates the liquid to increase its alcohol by volume. As liquors contain significantly more alcohol (ethanol) than other alcoholic drinks, they are considered "harder." In North America, the term hard liquor is sometimes used to distinguish distilled alcoholic drinks from non-distilled ones, whereas the term spirits is more commonly used in the UK. Some examples of liquors include vodka, rum, gin, and tequila. Liquors are often aged in barrels, such as for the production of brandy and whiskey, or are infused with flavorings to form flavored liquors, such as absinthe.