Lime juice is the juice of any one of a number of cultivars of the lime, a greenish fruit with a sour pulp and acidic juice. There are many different types of lime, with the most common being:

Citrus latifolia, also known as the Persian lime, the Tahiti lime, and the Bearss lime (after John Bearss, who developed it in 1895). These are the most common supermarket limes, and are seedless.

Citrus aurantifolia, also known as the Key lime or Bartender's lime. These are smaller and more yellow than the Persian lime, with many seeds and are not only highly acidic, but also interestingly bitter at the same time. 

Citrus hystrix, also known as the Kaffir lime, or Makrut lime. These are about as small as the Key Lime, but have a warty skin and are intensely sour. The kaffir lime (both zest and especially leaves) are commonly used in Malaysian and Thai cooking, but the juice is more commonly used as a cleanser. 

All lime juice is sour, having a pH of between 1.8 and 2, which makes it more sour than [ingredient=lemon-juice lemon juice]. For cocktail usage, the lime's strong green, grassy aspect works well with herbal flavors (think [ingredient=gin gin] and Green [ingredient=chartreuse Chartreuse]). It is not as neutral of an acidifier as lemon juice. 

Some popular cocktails containing Lime juice

  • Black Bowtie Gimlet — Gin, Bitters, Lime juice, Simple syrup, Squid ink, Salt Solution
  • Medicinal Sour — Herbal liqueur, Suze, Absinthe, Lime juice, Lemon juice, Anise syrup
  • Bernheim Buck — Wheat Whiskey, Strawberry, Ginger beer, Simple syrup, Lime juice, Lime
  • The Antioxidant — Cranberry Vodka, Aperol, Tangerine juice, Simple syrup, Lime juice, Strawberry, Orange peel
  • Fig Bee's Knees — Gin, Bitters, Honey syrup, Lime juice
  • Bogged Down Mule — Bison grass vodka, Cranberry liqueur, Bitters, Ginger beer, Lime juice, Simple syrup
  • Song to the Siren — Jamaican rum, Port, Swedish Punsch, Virgin Islands Rum, Bitters, Lime juice, Cinnamon syrup, Nutmeg
  • Old Painless is Waiting — Light rum, CuraƧao, Absinthe, Coconut Water, Lime juice, Pineapple syrup, Nutmeg
  • Gilded Paloma — Tequila, Soda water, Grapefruit juice, Pineapple juice, Lime juice, Cinnamon syrup, Grapefruit peel
  • Countrypolitan — Corn Whiskey, Triple sec, Lime juice, Cranberry juice