What type of cocktail is a "Sour"?

A "Sour" cocktail is defined primarily by its use of citrus juice, which is a key component in the mix. The addition of citrus juice, such as lemon or lime, not only provides a refreshing flavor but also contributes acidity, balancing the sweetness of other ingredients such as spirits or syrups. This combination creates the signature tartness that characterizes Sour cocktails, making them popular choices in the bartending world.

While some Sour cocktails might be served over ice or could have elements that might make them taste bitter, these are not defining characteristics of the Sour category itself. Additionally, cream-based cocktails fall under a different classification and do not align with the essential traits of a Sour. Therefore, the presence of citrus juice is the defining factor for identifying a cocktail as a "Sour."