Gin

Gin is a spirit which derives its predominant flavour from juniper berries (Juniperus communis). From its earliest origins in the Middle Ages, gin has evolved over the course of a millennium from a herbal medicine to an object of commerce in the spirits industry. Gin was developed on the basis of the older Jenever, and become widely popular in Great Britain when William of Orange, leader of the Dutch Republic, occupied the British throne with his wife Mary. Today, the gin category is one of the most popular and widely distributed range of spirits, and is represented by products of various origins, styles, and flavour profiles that all revolve around juniper as a common ingredient. 

Juniper-flavoured spirit drinks This includes the earliest class of gin, which is produced by pot distilling a fermented grain mash to moderate strength (e.g. 68% ABV), and then redistilling it with botanicals to extract the aromatic compounds. It must be bottled at a minimum of 30% ABV. Juniper-flavoured spirit drinks may also be sold under the names Wacholder or Genebra.

Gin
This is a juniper-flavoured spirit made not via the redistillation of botanicals, but by simply adding approved natural flavouring substances to a neutral spirit of agricultural origin. The predominant flavour must be juniper.

Distilled gin
Distilled gin is produced exclusively by redistilling ethyl alcohol of agricultural origin with an initial strength of 96% ABV (the azeotrope of water and ethanol) in stills traditionally used for gin, in the presence of juniper berries and of other natural botanicals, provided that the juniper taste is predominant. Gin obtained simply by adding essences or flavourings to ethyl alcohol of agricultural origin is not distilled gin.

London gin
London gin is obtained exclusively from ethyl alcohol of agricultural origin with a maximum methanol content of 5 grams per hectolitre of 100% ABV equivalent, whose flavour is introduced exclusively through the re-distillation in traditional stills of ethyl alcohol in the presence of all the natural plant materials used, the resultant distillate of which is at least 70% ABV. London gin may not contain added sweetening exceeding 0.1 grams of sugars per litre of the final product, nor colorants, nor any added ingredients other than water. The term London gin may be supplemented by the term "dry".

(Ingredient Description Reference: http://en.wikipedia.org/wiki/Gin)