Source : Webster's Revised Unabridged Dictionary (1913)

Invariable \In*va"ri*a*ble\, a. [Pref. in- not + variable: cf.
   F. invariable.]
   Not given to variation or change; unalterable; unchangeable;
   always uniform.

         Physical laws which are invariable.      --I. Taylor.
   -- {In*va"ri*a*ble*ness}, n. -- {In*va"ri*a*bly}, adv.

Source : WordNet®

invariableness
     n : the quality of being resistant to variation [syn: {invariability},
          {invariance}] [ant: {variability}, {variability}]