Source : Webster's Revised Unabridged Dictionary (1913)

Principally \Prin"ci*pal*ly\, adv.
   In a principal manner; primarily; above all; chiefly; mainly.

Source : WordNet®

principally
     adv : for the most part; "he is mainly interested in butterflies"
           [syn: {chiefly}, {primarily}, {mainly}, {in the main}]