Gin is a spirit whose predominant flavor is derived from juniper berries (Juniperus communis). Although several different styles of gin have existed since its origins, gin is broadly differentiated into two basic legal categories.
Distilled gin is crafted in the traditional manner, by re-distilling neutral spirit of agricultural origin with juniper berries and other botanicals.
Compound gin is made by simply flavoring neutral spirit with essences and/or other 'natural flavorings' without re-distillation, and is not as highly regarded. The minimum bottled alcoholic strength for gin is 37.5% ABV in the E.U., 40% ABV in the U.S.
There are several distinct styles of gin, with the most common style today being London dry gin, a type of distilled gin. In addition to the predominant juniper content, London dry gin is usually distilled in the presence of accenting citrus botanicals such as lemon and bitter orange peel, as well as a subtle combination of other spices, including any of anise, angelica root and seed, orris root, licorice root, cinnamon, cubeb, savory, lime peel, grapefruit peel, dragon eye, saffron, baobab, frankincense, coriander, nutmeg and cassia bark.
London dry gin may not contain added sugar or colorants, water being the only permitted additive.
Some legal classifications of gin are defined only as originating from specific geographical areas (e.g. Plymouth gin, Ostfriesischer Korngenever, Slovenská borovička, Kraški Brinjevec, etc.), while other common descriptors refer to classic styles that are culturally recognized but not legally defined (e.g. Old Tom gin).
In tropical British colonies, gin was used to mask the bitter flavor of quinine, which was the only effective anti-malarial compound. The quinine was dissolved in carbonated water to form tonic water, the resulting mix becoming the origin of today's popular gin and tonic combination, although modern tonic water contains only a trace of quinine as a flavoring.
Gin is a popular base spirit for many classic mixed drinks, including the martini.