Verbs are often flexible with regard to valency. In non-valency marking languages such as English, a transitive verb can often drop its object and become intransitive; or an intransitive verb can take an object and become transitive. For example, in English the verb "move" has no grammatical object in "he moves" (though in this case, the subject itself may be an implied object, also expressible explicitly as in "he moves himself"); but in "he moves the car", the subject and object are distinct and the verb has a different valency. Some verbs in English, however, have historically derived forms that show change of valency in some causative verbs, such as "fall-fell-fallen":"fell-felled-felled"; "rise-rose-risen":"raise-raised-raised"; "cost-cost-cost":"cost-costed-costed".