Bourbon is made using a minimum of 51% corn-based mash and has been distilled since the 18th Century.

The whiskey is barrel-aged in new charred oak and bottled at least 80% proof (or 40% abv), although it must enter the barrel for aging at no more than 125% proof (62.5% abv).

There is no restriction for aging – except for straight bourbon which must be aged for minimum of two years. All bourbon aged less than four years must include an age statement.

Bourbon production is not restricted to one state in the US, however it strongly associated with Kentucky.

Originally outlined in the 1897 Bottled In Bond Act, this statement means that the spirit must be the product of one distillation season (January-June or July-December) by one distiller at one distillery. Also, it must have been aged in a federally bonded warehouse under US Government supervision for at least four years and bottled at 100% proof (or 50% above to us in the UK!).

As with Bourbon, corn whisky has a minimum requirement for content of corn in its mash, however in this instance, it is at least 80% corn.

It is distilled to a maximum strength of 160% proof (80% abv) and must be barreled at less than 125% proof (62.5% abv) although law states it doesn’t have to be barrel aged.

Kentucky Straight Bourbon must fulfill two requirements;

1/ Be made in Kentucky, and;

2/ must be aged in new oak barrels for at least two years at an abv no more than 62.5%.

It’s the 2nd element is what defines ‘straight bourbon’ from just ‘bourbon’.

No modifications are allowed to the spirit (such as colouring) meaning that mixing barrels, filtering and dilution with water are the only things the distillery may do.

Not to be confused with a ‘straight’ whiskey – ie; one without water or a mixer..

Rye whiskey is produced in both America and Canada. In this section, American Rye, the whiskey must be distilled from at least 51% rye. The other ingredients in the mash are usually corn and malted barley.

Historically, Rye was commonly found from the northeastern states, such as Pennsylvania and Maryland. However, much of the production disappeared during prohibition.

Compared to Bourbon, Rye can be spicy and fruity.

Wheat whiskey must have a grain bill which is primarily wheat. To be labelled ‘wheat’, there must be at least 51% wheat in the mash.

As with Kentucky Straight Bourbon, the ‘straight’ element refers to a whiskey which is aged for at least two years in new, charred oak barrels, with no colouring added.

Tennessee whiskey is straight whiskey made in Tennessee. Often categorised as ‘Bourbon’ on drinks lists, enthusiasts and producers will go to lengths to ensure the specification is used correctly.

As well as being produced in Tennessee (except for Benjamin Prichard’s!), Tennessee whiskey should be filtered using the Lincoln County Process – where the spirit is either filtered through, or steeped in charcoal before going into casks for aging.

However, Bourbons are allowed to, and often use charcoal filtering, and additionally, Tennessee Whisky does not have a US Federal definition under the Standards of Identity for Distilled Spirits… Confusing, eh?)

A whiskey liqueur is still made from distilled spirit, however usually, but not always, has a lower alcohol content (such as 15-30% abv) and do not have to be aged for long periods of time.

Due to their flavouring – honey, fruit – they often have a sweet flavour, however a liqueur can be made with spices, coffee, herbs and even nuts.

In the USA, these can sometimes be referred to as a cordial or schnapps – but not to be mistaken with the European definition of these terms.