Normal people measure things in ounces, cups, tablespoons and other recognizable increments. Cocktail people often use “parts” instead, which puts the recipe in the form of a ratio.
A part can be any type of measurement. All you have to do is assign a measurement increment to be a part—for example, one part equals one ounce—then do a little bit of basic math.
Here’s an example of a recipe given in parts: