What does the term "sour" refer to in cocktail terminology?

The term "sour" in cocktail terminology primarily refers to a balance of sweet and acidic flavors. This concept is most famously embodied in cocktails like the Whiskey Sour or the Pisco Sour, where the combination of a spirit, a sour component (usually citrus juice, such as lemon or lime), and a sweetener (like simple syrup) creates a well-rounded flavor profile. The acidic elements provide brightness and freshness, countering the sweetness to achieve harmony in taste. This balance is essential for creating refreshing and enjoyable cocktails, as the interplay between sweetness and acidity is fundamental in many classic drinks.