Whiskey Styles Compared

Attribute	Bourbon	Rye	Scotch	Irish Whiskey	Japanese Whisky
Primary Grain	Minimum 51% corn in the mash bill	Minimum 51% rye in the mash bill	Malted barley (single malt), or malted barley plus other cereal grains (single grain / blended)	Malted barley (single malt); malted plus unmalted barley (single pot still); or a mix of cereals (single grain)	Malted grain required; other cereal grains may also be used
Still Type	Column still, typically finished through a doubler/thumper pot still	Column still, typically finished through a doubler or thumper pot still	Pot stills for single malt; continuous column stills for single grain	Pot stills for malt and single pot still styles; column stills for grain whiskey; varies by category	Historically Scotch-influenced; pot stills for malt whisky, column stills for grain whisky; though still type isn't itself mandated by the labeling standard below
Barrel Requirement	New, charred oak containers only; never reused	New, charred oak containers only; never reused	Oak casks only, 700 liters or smaller; but reuse is standard. Most Scotch matures in previously used ex-bourbon or ex-sherry casks, not new wood.	Wooden casks only, 700 liters or smaller. New or previously used oak are both allowed.	Wooden casks only, 700 liters or smaller, aged in Japan
Minimum Aging	No federal minimum for bourbon itself. "Straight" bourbon requires at least 2 years; under 4 years requires an explicit age statement.	No federal minimum for rye whiskey itself. Straight rye requires at least 2 years; under 4 years requires an explicit age statement.	At least 3 years, aged in oak casks in Scotland	At least 3 years, aged in wooden casks on the island of Ireland	At least 3 years; but this is a voluntary industry labeling standard (Japan Spirits & Liqueurs Makers Association, effective April 2021), not a government law. Before 2021, "Japanese Whisky" had no legal aging requirement at all, and some bottles sold under that name were partly or entirely imported bulk whisky.
Spelling Convention	Whiskey	Whiskey	Whisky	Whiskey	Whisky

Primary Grain

Bourbon: Minimum 51% corn in the mash bill
Rye: Minimum 51% rye in the mash bill
Scotch: Malted barley (single malt), or malted barley plus other cereal grains (single grain / blended)
Irish Whiskey: Malted barley (single malt); malted plus unmalted barley (single pot still); or a mix of cereals (single grain)
Japanese Whisky: Malted grain required; other cereal grains may also be used

Still Type

Bourbon: Column still, typically finished through a doubler/thumper pot still
Rye: Column still, typically finished through a doubler or thumper pot still
Scotch: Pot stills for single malt; continuous column stills for single grain
Irish Whiskey: Pot stills for malt and single pot still styles; column stills for grain whiskey; varies by category
Japanese Whisky: Historically Scotch-influenced; pot stills for malt whisky, column stills for grain whisky; though still type isn't itself mandated by the labeling standard below

Barrel Requirement

Bourbon: New, charred oak containers only; never reused
Rye: New, charred oak containers only; never reused
Scotch: Oak casks only, 700 liters or smaller; but reuse is standard. Most Scotch matures in previously used ex-bourbon or ex-sherry casks, not new wood.
Irish Whiskey: Wooden casks only, 700 liters or smaller. New or previously used oak are both allowed.
Japanese Whisky: Wooden casks only, 700 liters or smaller, aged in Japan

Minimum Aging

Bourbon: No federal minimum for bourbon itself. "Straight" bourbon requires at least 2 years; under 4 years requires an explicit age statement.
Rye: No federal minimum for rye whiskey itself. Straight rye requires at least 2 years; under 4 years requires an explicit age statement.
Scotch: At least 3 years, aged in oak casks in Scotland
Irish Whiskey: At least 3 years, aged in wooden casks on the island of Ireland
Japanese Whisky: At least 3 years; but this is a voluntary industry labeling standard (Japan Spirits & Liqueurs Makers Association, effective April 2021), not a government law. Before 2021, "Japanese Whisky" had no legal aging requirement at all, and some bottles sold under that name were partly or entirely imported bulk whisky.

Spelling Convention

Bourbon: Whiskey
Rye: Whiskey
Scotch: Whisky
Irish Whiskey: Whiskey
Japanese Whisky: Whisky