Typically based upon a neutral grain spirit
Then redistilled with various botanicals
London Dry is the most common
Gin is a spirit that is typically triple distilled, based upon grain spirits, and cut with distilled water. In most cases, the grain spirits have been created through a double or triple column still distillation. Then the grain spirit is distilled a final time in a pot still with botanicals including juniper, oil of juniper, coriander, orange peel, lemon peel, anise, cassia, bitter almonds, caraway, cocoa, angelica root, orris root, and many other ingredients. Producers zealously guard their botanical recipes.
Gin can be made anywhere that distillation occurs. Still, there are four approximate types of gins and they tend to come from certain places.
London Dry Gin needn't come from London and for nearly the last two centuries the majority of gin producers have looked to London Dry Gin as the benchmark gin style. It is made all around the world, but the style is nonetheless associated with Great Britain. Citrus fruits and/or juniper tend to dominate. Alcohol range tends to be from 40 to 47 percent by volume. Has to be predominantly juniper in flavor and nothing added after distillation.
Genever or Hollands Gin is rarely produced outside of Holland. It has some yellowish color, may be distinctly sweet, in opposition to London Dry, and can be powerful and oily.
Plymouth, England is home to a single gin distillery and a distinctive style, called Plymouth. Plymouth Gin is lower in alcohol than London Dry varieties but owns an earthy richness that is unique. Abv is 41.2 percent.
New Style gins (some say New American gins) are as diverse as the many places from which they derive. Alcohol range is from 40 to 55 percent by volume. (Hendricks, Bombay Sapphire, Tanqueray 10)
Key Points & Opinion
Juniper is the botanical of note
London Dry Gin is what most people think of when they think of gin
Beefeater (London Dry)
Plymouth Gin (Plymouth)
Junipero (New Style)