Don't be confused if you're looking at a drink recipe and it doesn't give an exact measurement. The phrase "one part" simply lets you know the ratio of each ingredient. It gives you the freedom to make a single mixed beverage or a large batch at once, without having to whip out your measuring devices or do any mathematical calculations.
How It Works
One part is an inexact measurement. It can mean, for example, 1 ounce, 1 tablespoon or 1 cup. The key is keeping all "parts" equal. So if your drink calls for one part alcohol and three parts juice and you're making a drink for yourself, you'd want a mixture of 1 ounce of liquor and 3 ounces of the juice. But you can make it larger as well. To make a pitcher of the same drink, increase the volume to something like one fluid cup of liquor and three fluid cups of juice. As long as all parts follow the same unit of measurement -- even if your unit of measurement is a coffee mug -- your drink recipe will come out the same every time.