Irregularity :: Irregularity (n.) The state or quality of being irregular; that which is irregular.
Regularia :: Regularia (n. pl.) A division of Echini which includes the circular, or regular, sea urchins..
Regularity :: Regularity (n.) The condition or quality of being regular; as, regularity of outline; the regularity of motion..
Regularize :: Regularize (v. t.) To cause to become regular; to regulate.