What is the difference between Scotch, Irish, Rye and Bourbon Whiskies?

Scotch Whisky is whisky, which has been distilled and matured in Scotland. Irish Whiskey means whiskey distilled and matured in Ireland. Whisky is distilled in Scotland from malted barley in Pot Stills and from malted and unmalted barley or other cereals in Patent Stills. The well-known brands of Scotch Whisky are blends of a number of Pot Still and Patent Still whiskies. Irish Whiskey distillers tend to favour three distillations rather than two, as is general in Scotland in the case of Pot Still whiskies and the range of cereals used is wider.
As regards Bourbon Whiskey, the United States Regulations provide:
1. that Bourbon Whiskey must be produced from a mash of not less than 51% corn grain;
2. that the word 'Bourbon' shall not be used to describe any whiskey or whiskey-based distilled spirits not produced in the United States.
Rye Whiskey is produced both in the United States and Canada but the name has no geographical significance. In the United States, Rye Whiskey by definition must be produced from a grain mash of which not less than 51% is rye grain. In Canada, there is no similar restriction. The relevant Canadian Regulation states: 'Canadian Whisky (Canadian Rye Whisky, Rye Whisky) shall be whisky distilled in Canada and shall possess the aroma, taste and character generally attributed to Canadian Whisky.'
Canadian Whisky is in fact often referred to simply as Rye Whisky or Rye.