Source : Webster's Revised Unabridged Dictionary (1913)

Regularity \Reg`u*lar"i*ty\ (-l?r"?*t?), n. [Cf. F.
   r['e]gularit['e].]
   The condition or quality of being regular; as, regularity of
   outline; the regularity of motion.

Source : WordNet®

regularity
     n 1: a property of polygons: the property of having equal sides
          and equal angles [syn: {geometrical regularity}]
     2: the quality of being characterized by a fixed principle or
        rate; "he was famous for the regularity of his habits"
        [ant: {irregularity}]