its just same meaning as to noun. 1.Status established in order of importance or urgency "...its precedence as the world's leading manufacturer of pharmaceuticals" 2.Preceding in time 3.The act of preceding in time or order or rank (as in a ceremony) cowboy...

Both precedence and precedency have the same meaning ( nouns) antecedence, ante-position, earliness, lead, precession, preeminence, preexistence, preference, primary, priority, rank*, right of way, seniority, superiority, supremacy