Gin is a clear distilled spirit flavoured with a variety of herbs, roots and spices, known as botanicals. In the UK and EU, in order to be called a gin a spirit must have a minimum strength of 37.5% alcohol and juniper must be the dominant botanical.

Gin production starts with a neutral base spirit. Usually, this is a spirit distilled in a continuous (column) still to a very high percentage of alcohol (95-96%), although some producers use a pot still or Lomond still spirit as their base. 

The most common neutral spirit is Neutral Grain Spirit (NGS) which is produced from grains such as wheat, corn, rye, spelt, barley or rice. Other neutral spirits may be distilled from crops including potatoes, grapes, sugar beet and molasses, although molasses-based spirits are rarely used for gin production due to their stronger aromas and flavours - most gin and vodka producers are looking for a base that is as flavourless as possible.

The majority of gins use a mix of at least half a dozen botanicals, although some producers such as The Botanist or Monkey 47 use many more. Aside from juniper, classic gin botanicals include cardamom, nutmeg, coriander, cassia, orris root, ginger, angelica, liquorice, orange / lemon peels, star anise, cubeb and black pepper.

Depending on their individual characteristics and the producer’s stylistic (or economic) requirements, the flavours from individual botanicals may be added to gin’s neutral spirit base by addition of flavourings and essences, or by maceration, where fresh or dried botanicals are steeped in the neutral spirit. Gins produced this way without separate distillation are known as Compound Gins. During Prohibition in the US in the 1920s, many people made low-quality compound gins in their baths, leading to the derogatory term Bathtub Gin.

Higher quality gins are usually distilled or redistilled with their botanicals and are known as Distilled Gin. The botanicals are steeped in neutral spirit and redistilled, either together or individually, with the resulting separate botanical spirits blended together to make the gin. Some specialist gin stills contain a suspended mesh basket for botanicals within the still or between the still and the condenser, enabling the spirit’s vapour to be infused with botanical flavours as it is redistilled.

In recent years some producers have begun using vacuum distillation for more delicate botanicals, arguing that the lower temperatures required for this type of distillation are gentler on the botanicals and enable them to extract a purer flavour.

The most popular type of gin is London Dry, a juniper-forward style dry gin made with the classical botanicals. Other classic styles of gin include the historical Jenever, a Dutch precursor to gin often made with malt or grape spirit from which modern gin gets its name, and Old Tom, a sweetened gin style popular in the 19th century.

Many modern gins have a less juniper-heavy flavour profile and the recent surge in gin's has led to an increase in innovation, with new and exotic botanicals appearing all the time.