Source : Webster's Revised Unabridged Dictionary (1913)

Permanence \Per"ma*nence\, Permanency \Per"ma*nen*cy\, n. [Cf.
   F. permanence.]
   The quality or state of being permanent; continuance in the
   same state or place; duration; fixedness; as, the permanence
   of institutions; the permanence of nature.

Source : WordNet®

permanency
     n : the property of being able to exist for an indefinite
         duration [syn: {permanence}] [ant: {impermanence}]