precedent, precedence

The meaning of the word precedent in law—a judicial decision that sets a rule—is very close to the common usage of the word: an “example” or “custom resulting from long practice.” A lawyer might find several precedents, that is, a number of cases ruling on the same point.

Precedence is generally used as a synonym for “priority” or “rank.”

Example: They set a bad precedent when they chose to give precedence to their friends’ applications first.