Well, for over a century, what goes on a whiskey bottle’s label has been defined by governments. Scotland has its own definitions, Ireland has its preferred wording, and so forth.
In the United States, the Code of Federal Regulations provides the definitions of the various types of whiskey.
AlcoholReviews.com has produced an image of these definitions that you see for yourself by clicking here. (Your web browser might render the image so that the text is real tiny, but have no fear, you need only click on the image to make the text grow in size.)