Single malt Scotch is single malt whisky made in Scotland. To be a single malt scotch the whisky must have been distilled at a single distillery using a pot still distillation process and made from a mash of malted grain. In Scotland, the only grain allowed to be used in a single malt whisky is barley. As with any Scotch whisky, a single malt Scotch must be distilled in Scotland and matured in oak casks in Scotland for at least three years. (Most single malts are matured longer.)
"Malt" indicates that the whisky is distilled from a "malted" grain. Several types of grains can be malted (for example, barley, rye and wheat are all grains which can be malted); however, in the case of single malt Scotch, barley is always the only grain used.
"Single" indicates that all the spirits in the bottle come from a single distillery. Bottlings containing malt whisky from multiple distilleries are called "blended malt".
Single malt whisky is malt whisky from a single distillery, that is, whisky distilled from fermented mash made exclusively with malted grain, as distinguished from unmalted grain. There is no definition of the term single with relation to whisky in the law of the United States, and some American whiskey advertised as single malt whisky is produced from malted rye rather than malted barley.