Precedence: the fact or act of preceding, as in The first patent application receives precedence in Europe; priority in place, time, or rank because of superiority, as in The company relied on its precedence as the leading producer of computer chips; a ceremonial rank or preference.
Precedent: in law, a judicial or other legal decision that establishes a rule to be followed by lower courts or tribunals; any decision or act that serves as a guide.
Precedential: having precedence, usually because of longer service; having the character of a precedent or guide.
The man who will follow precedent, but never create one, is merely an obvious example of the routineer [a person who follows routine]. You find him desperately numerous in the civil service, in the official bureaus. To him government is something given as unconditionally, as absolutely as ocean or hill. He goes on winding the tape that he finds. His imagination has rarely extricated itself from under the administrative machine to gain any sense of what a human, temporary contraption the whole affair is. What he thinks is the heavens above him is nothing but the roof.
—Walter Lippmann A Preface to Politics (1913)