You hear it in some recipes, you hear it in some ingredient addons. And you even hear it when your teachers in class do it. But what exactly is a “part”. It’s not really a valid unit of measurement but more of those “Rule of Thumb” deals isn’t it.
For all anyone knows, a ‘part’ could range from one teaspoon to twenty thousand gallons. For the record, just use actual measurements when sharing this stuff to others, it would spare you from looking like an idiot.