المعنى الاصطلاحي :

When someone who is competent for religious assignment commits himself to a certain act of worship that is not binding upon him according to the Shariah

الشرح المختصر :

"Nadhr" (vow) means that someone who is competent for religious assignment commits himself to a certain act of worship which is not binding on him in the Shariah. An example is when one makes a "nadhr" to fast or give a certain amount of charity; it is obligatory on him to fulfill his "nadhr". There are two types of "nadhr": 1. A general "nadhr": when one commits himself to performing an act of worship for the sake of Allah, the Almighty, without stating a condition, like saying, for instance: "I vow to pray two "rak‘ahs" (units of prayer) for the sake of Allah." This "nadhr" is not made in return for something that should happen to him in the future or something that has already happened to him. 2. A restricted "nadhr": when one commits himself to performing an act of obedience for the sake of Allah, the Almighty, in return for something that Allah ordains for him and causes it to happen. An example is when one says: "If Allah heals my patient, I vow to give such-and-such as charity."

التعريف اللغوي المختصر :

"Nadhr": obliging oneself, making a vow to Allah voluntarily to perform a certain act of worship or to give charity or the like.