Same word as natural:

accustomed, anticipated, characteristic, common, commonplace, congenital, connatural, consistent, constant, counted on, customary, essential, familiar, general, habitual, inborn, indigenous, ingenerate, inherent, innate, instinctive, intuitive, involuntary, legitimate, logical, looked for, matter-of-course, natal, native, ordinary, prevailing, prevalent, probable, reasonable, regular, relied on, spontaneous, typic, typical, unacquired, uncontrolled, uniform, universal, usual