Vow
Vow means making it obligatory upon oneself to do some good act, or to refrain from doing an act, which it is better not to do, in order to please Allah.
Useful information: While making a vow one should utter the formula and it is not necessary that it should be uttered in Arabic. In case. therefore, a person says: "If my patient recovers from his ailment, it will be obligatory upon me to pay $ 10 to a poor man for the sake of Allah." his vow will be in order.