How is bourbon different from whiskey?

Bourbon is whiskey. The question is the same shape as asking how a Granny Smith is different from an apple: bourbon is one kind, and "whiskey" is the family it belongs to. Specifically, bourbon is an American whiskey made mostly from corn and aged in new charred oak barrels, and a short list of federal rules decides which whiskeys get to wear the name. Those rules aren't arbitrary trivia. Six of them, taken together, are the reason bourbon tastes like bourbon and not like Scotch.

What are the rules that make a whiskey a bourbon?

A whiskey has to clear every rule in the table below to be sold as bourbon in the United States. Each rule does two jobs: it pins down something about how the spirit is made, and it rules out a familiar style of whiskey that breaks it.

Rule	What it requires	What it excludes
Origin	Made in the United States	Scotch, Irish whiskey, Japanese whisky, Canadian whisky
Mash bill	At least 51% corn in the grain recipe	Rye, malt, and wheat whiskeys built on a different grain
Distillation proof	Distilled to no more than 160 proof (80% ABV)	Lighter, neutral-style spirits distilled higher
Barrel	Aged in new, charred oak barrels	Any whiskey aged in used casks, including Scotch
Bottling proof	Bottled at 80 proof (40% ABV) or higher	Diluted, lower-strength whiskeys
Additives	No coloring, flavoring, or other additives	Flavored whiskeys and whiskeys with caramel coloring

"Mash bill" is just the recipe of grains that go into fermentation. The 51% corn rule sets the floor; most bourbons run between 60% and 80% corn, with the remaining slot filled by rye, wheat, or malted barley, which is where high-rye and wheated bourbons get their names.

A few other labels stack on top of this base rule set. "Straight bourbon" has to be aged for at least two years. "Bottled-in-bond" has to be aged for at least four years, distilled in one season at one distillery, and bottled at exactly 100 proof. "Kentucky bourbon" has to be made in Kentucky. None of those are required for a spirit to be called bourbon. The six rules in the table are.

If bourbon is whiskey, what are the other kinds of whiskey?

Bourbon shares the shelf with several other whiskey traditions, each defined by its own rules and region. The names are easier to keep straight once you know each one is just another corner of the same family.

Bourbon and rye are the two American whiskey traditions most newcomers run into first, and they sit closer to each other than either does to anything made overseas. Rye is the mirror image of bourbon: same federal framework, but the mash bill has to be at least 51% rye instead of 51% corn, which trades bourbon's sweetness for a sharper, spicier profile.

Scotch is whisky made in Scotland, usually from malted barley, and aged in used casks rather than new ones. The reused barrels are why Scotch picks up subtler wood character than bourbon does, and they're also why some single malts taste like sherry or port: the cask had sherry or port in it first.

Irish whiskey is made in Ireland and is typically distilled three times rather than two, which produces a lighter spirit. It's most often a blend of grain whiskey and pot still whiskey, though single malt Irish whiskey exists too.

Tennessee whiskey meets every rule for bourbon and then adds one of its own: the spirit is filtered through charcoal before barreling, a step called the Lincoln County Process. By federal standards Tennessee whiskey is bourbon. The state and the producers prefer to file it under its own name.

Canadian whisky is made in Canada and is usually a blend of separately distilled grain whiskies, with rye historically common in the mix. Japanese whisky is made in Japan and follows the Scotch tradition closely, since the Japanese industry was founded by distillers who trained in Scotland.

Scotch and bourbon differ on almost every variable that matters: grain, cask, region, distillation, and flavor, which makes it the cleanest cross-tradition comparison to start with.

Why do these specific rules make bourbon taste like bourbon?

The rules aren't a heritage formality. Two of them, the corn-heavy mash bill and the new charred oak barrel, are doing most of the flavor work, and changing either one would make the spirit taste like something else.

Corn is a sweeter grain than barley or rye. It ferments into a wash that carries more sugar, and that sweetness survives distillation into the unaged spirit. Bourbons with very high corn content (90% or more) read as round and almost dessert-sweet on the palate. Bourbons closer to the 51% floor, with more rye or wheat in the mash bill, trade some of that sweetness for spice or softness.

The new charred oak rule is the bigger lever. Before barreling, the inside of the cask is set on fire long enough to leave a layer of black, alligator-cracked char on the wood. The heat from charring breaks down compounds inside the oak, and the ones that matter most for flavor taste like vanilla, caramel, toffee, butterscotch, and coconut. As the bourbon expands into the wood during hot weather and contracts back out in the cold, it pulls those compounds out of the char layer and carries them in solution. The vanilla and caramel notes most people associate with bourbon are coming directly out of the burned wood.

The new-barrel part of the rule is what makes this hit so hard. A fresh charred barrel has a full reservoir of those compounds and gives them all to one batch of whiskey. A used barrel, like the casks Scotch is aged in, has already donated most of its flavor to a previous spirit and contributes a much subtler wood character to the next one. Bourbon's bold sweet-and-oak profile is what one whiskey tastes like when it gets a brand-new barrel to itself.

Did you know? The new-barrel rule is also why Scotch tastes the way it does. American distillers can't reuse their bourbon barrels to make more bourbon, so they sell the empty casks to Scotland, where most Scotch whisky is aged in them. The American rule that forces fresh oak on bourbon is the same rule that supplies Scotland with its used oak.

Does bourbon have to be from Kentucky?

No. Federally, bourbon can be made anywhere in the United States. Texas, New York, Colorado, California, and Indiana all have distilleries producing bourbon today, and a few of them ship product nationally. The only place geography enters the federal rules is the requirement that the spirit be made somewhere in the US.

Kentucky shows up in almost every conversation about bourbon for a real reason, though. Around 95% of the world's bourbon is made in Kentucky, by volume. The state's limestone-filtered water is naturally low in iron (which would react badly with the fermentation) and high in calcium (which yeast feeds on well). The temperature swings between Kentucky summers and winters drive the spirit in and out of the barrel hard, which speeds up the interaction with the char layer. And the major brand names most newcomers recognize, like Buffalo Trace, Maker's Mark, Wild Turkey, and Jim Beam, are all Kentucky distilleries.

What Kentucky does claim is the term "Kentucky bourbon." A bourbon labeled "Kentucky" or "Kentucky Straight Bourbon" has to be distilled and aged in Kentucky. The rest of the word "bourbon" is open territory.

The honest way to read any bourbon bottle is to look at what actually defines the spirit: what grains are in the mash bill, how long it sat in the cask, and where it was made. The state on the label tells you something about tradition and odds, but it isn't what makes a bourbon a bourbon. The six rules in the table are.