The lime is a citrus fruit that is smaller and sweeter than its close relative, the lemon. Limes are a very common ingredient in Mexican, Vietnamese, Indian, and Thai cuisines and help enhance the flavor of countless dishes and drinks. In the 19th century, British sailors were given lemons and limes daily to prevent scurvy (because of their high vitamin C content); that's how the British earned the nickname "limeys". (Read more on Wikipedia.)