Single Malt is a whisky made at just one single distillery and is made using malted barley, yeast and water. It may be made up of several different casks from that one distillery. It may be made anywhere in the world but if it is not from Scotland it cannot be called Scotch single malt whisky. Within the category you also have single cask single malt whisky, which is whisky from just one cask, and cask strength single malt whisky which is bottled at the strength when it comes out of the cask, normally much higher than a normal bottling strength.