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®

invariably
     adv : in an invariable manner; "invariably, he would forget his
           keys"