What is one characteristic of a sour cocktail?

A sour cocktail is defined primarily by its use of citrus juice, which is a key ingredient that contributes to the drink's distinctive tartness. Citrus juices like lemon or lime are essential components in sour cocktails, balancing the sweetness of other ingredients such as sweeteners or liqueurs. This combination creates a refreshing and well-rounded flavor profile that characterizes the sour category of cocktails.

The presence of citrus not only adds complexity to the taste but also enhances the overall drinking experience by providing acidity, which is crucial for cutting through richer flavors in the drink. Therefore, the defining characteristic of a sour cocktail is its inclusion of citrus juice, which sets it apart from other cocktail styles that might lean more toward bitterness or sweetness.