Source : Webster's Revised Unabridged Dictionary (1913)

Constancy \Con"stan*cy\, n. [L. constantia: cf. F. constance.
   See {Constant}.]
   1. The state or quality of being constant or steadfast;
      freedom from change; stability; fixedness; immutability;
      as, the constancy of God in his nature and attributes.

   2. Fixedness or firmness of mind; persevering resolution;
      especially, firmness of mind under sufferings, steadiness
      in attachments, or perseverance in enterprise; stability;
      fidelity.

            A fellow of plain uncoined constancy. --Shak.

            Constancy and contempt of danger.     --Prescott.

   Syn: Fixedness; stability; firmness; steadiness; permanence;
        steadfastness; resolution. See {Firmness}.

Source : WordNet®

constancy
     n 1: the quality of being free from change or variation [syn: {stability}]
          [ant: {inconstancy}]
     2: the tendency for perceived objects to give rise to very
        similar perceptual experiences in spite of wide variations
        in the conditions of observation
     3: faithfulness in personal attachment (especially sexual
        fidelity)