المعنى الاصطلاحي :

Allah's ordainment a certain act to be done by way of obligation.

الشرح المختصر :

Wujūb (obligation) is an obligation laid down by the Almighty Lawgiver, be it verbal, like mentioning the name of Allah when slaughtering an animal; physical, like offering the prayer at its appointed time; or done by the heart, like believing in Allah, the Almighty. Obligation is divided into numerous types: 1. Depending on the person subject to the obligation, it is either individual or collective. An individual obligation, like the prayer, is due on each and every person. A collective obligation, on the other hand, is ordained on a group of people, and if some of them do it adequately, it ceases to be due on the others. An example is the funeral prayer. 2. Depending on whether the obligation is specified or not, the specified is called "mu‘ayyan", like the five obligatory prayers; the unspecified is called "mukhayyar", the types of kaffārah (expiation). 3. Depending on the time limit, the obligation should either be performed as promptly as possible, like the Hajj, or it can be conveniently delayed and performed in a broad time frame, such as making up for missed days of fasting in Ramadan. 4. Depending on action's relation to time, whereby it is classified to wājib muwassa‘ (non time-limit obligation) in which more than one obligation can be performed such as the five obligatory prayers, and wājib mudayyaq (time-limit obligation) in which only one obligation can be performed such as fasting the month of Ramadan.

التعريف اللغوي المختصر :

"Wujūb": obligation, requirement. Original meaning: falling. Other meanings: firmness, stability.