Source : Webster's Revised Unabridged Dictionary (1913)

Primacy \Pri"ma*cy\, n. [LL. primatia, fr. L. primas, -atis, one
   of the first or principal, chief, fr. primus first: cf. F.
   primatie. See {Prime}, a.]
   1. The state or condition of being prime or first, as in
      time, place, rank, etc., hence, excellency; supremacy.
      [R.] --De Quincey.

   2. The office, rank, or character of a primate; the chief
      ecclesiastical station or dignity in a national church;
      the office or dignity of an archbishop; as, the primacy of
      England.

Source : WordNet®

primacy
     n : the state of being first in importance