London Dry, which is the style I assume you are asking about, is the most prevalent gin on the market. If you’re a gin drinker, it is more than likely that the gin you’re drinking is one that’s made in this style. These gins often feature a balanced base of juniper and citrus, and they are so-called London Dry because when this style was created, it differed from the two older styles of the spirit — most specifically, Old Tom and Genever.
Genever is the oldest style of gin, dating all the way back to 16th-century Holland. Genever uses at least 15 percent malt, which gives it a more viscous mouthfeel. This viscosity comes from the sugar in the malt.
Old Tom, on the other hand, is a gin containing sweetener, often from licorice, which is added during the distillation. There are not many styles of Old Tom on the market, but it’s gaining in popularity, especially among bartenders who believe this style stands up much better to the bitter flavors in some classic gin cocktails.
Other styles of gin also now abound, including modern takes on gin such as Hendricks — also dry — fruit flavored gins; Plymouth gin, which can only be made in Plymouth, England; and gins made from all sorts of bases, including grapes and even whey. But if you’re looking for the most well-known alternatives to the classic London Dry, Old Tom and Genever will always be the two clearest examples.