All whisky is categorized by Material and Blending.
Additionally another world whiskies (Scotch, Irish, Bourbon/American and Canadian) is defined by strict PDO (protected designation of origin) which has specific requirement about not only above 2 points (material and blending) but also process, process location and aging.
Malt whisky is made from only malt without any other grains.
Grain whisky use not only grain but also malt because mashing grain require enzyme which malt contains. (Other grain doesn't have enzyme) Grain means non-malted barley, corn, wheat and oat.
Blended whisky is blended of malt whisky and grain whisky which were aged in different barrel. But blended in American whisky is different meaning.
Some rice whisky distilleries claim that rice is also grain but it should be categorized differently. Because most of them are 100% rice and mashing is done by Koji instead of malt enzyme.
Except for single cask bottle and cask strength bottle, almost all whisky bottle are blended of several different cask whisky.
Single malt and Single grain are made from several cask whisky distilled by same distillery.
There are some variation by material and blending.
Aging Category and description
Aged years description on bottle label
Years described on bottle label is youngest material whiskies. So Yamazaki 18 years contains only 18 years aging material whisky or older one.
Minimum year requirement of each TGI whisky
Each TGI regulation(Like scotch, bourbon and etc) also requires minimum aging years.
Shorter than TGI requirement
Bottled with shorter time aging than TGI requirement is called "New Born".
Bottled just after distillation without aging is called "New Make" or "New Pot".
World whisky category
There are 5 world whiskies including Japanese. The others are Scotch, Irish, Canadian and American including Bourbon. These 4 whiskies have strict PDO (protected geographical indication) regulation.