
Ibn Syed,
Shaykh Muhammad Ali Al-Hanooti has mentioned:
1) al Wajib as a general term in Usul al Fiqh refers to what is obligatory. For the majority of schools al wajib is the same as a fard.
2) The Hanafi School differentiates between fard and wajib. Fard for them means the obligation is certain and based on clear-cut evidence. Usually it is understood by Quran or Hadith mutawatir or similar to the mutawatir.
3) Sunnah in fiqh refers to what is optional. In hadith it refers to what the Prophet does, says, or approves.
Most schools of fiqh classify all obligatory things as waajib, and then divide that into fard ayn (individual obligation) or fard kifaayah (collective obligation).
However, some scholars of fiqh classify waajib as a lesser degree in comparison to fard. For example, it is Fard to pray your five daily prayers but only waajib to pray Witr (prayer after Isha) and waajib to pray Eid Salat. The beard has been classified by these scholars as Waajib as well. In this case, waajib refers to something that is more important than "Sunnah" but less important than "Fard".
I have an article by
Shaykh Abdur-Rahman As-Sa'dee on some terms in fiqh, although it might be a bit technical. He goes by the first opinion that Waajib is the same as fard, and is just a general term for Fard.
The ahkaam (rulings) upon which fiqh revolve are five:-
[1]: Waajib (obligation): that for which the one who performs it is rewarded, whilst the one who abandons it is punished.
[2]: Haraam (prohibition): this is the opposite of an obligation.
[3]: Masnoon (recommended): that for which the one who performs it is rewarded, whilst the one who leaves it is not punished.
[4]: Makrooh (detested): this is the opposite of a recommendation.
[5]: Mubaah (permissible): this is where both (its doing or leaving) are equivalent.
Those rulings which are waajib (obligatory) are divided into two catagories: fard ’ayn (individual obligation), the doing of which is sought from every mukallaf (morally responsible), baaligh (mature) ’aaqil (sane) person. The majority of the Sharee’ah rulings enter into this catagory. The second is fard kifaayah (collective obligation), the performance of which is sought from the morally responsible collectively, but not from every individual specifcally; such as the learning of the various branches of useful knowledge and useful industries; the adhaan; the commanding of good and forbidding of evil; and other similar matters.
These five rulings differ widely in accordance with its state, its levels and its effects.
Thus, whatever is of pure or of overwhelming maslah (benefit), then the Shaari’ (Lawgiver) has commanded its performance with either an obligation or a recommendation. Whatever is of pure, or of overwhelming mafsadah (harm), then the Lawgiver has stopped its doing with either an absolute prohibition or dislike. So this asl (fundamental principle) encompasses all matters commanded of prohibited by the Lawgiver.
As for those matters which the Lawgiver has permitted and allowed, then at times they lead to that which is good, and so are joined to those matters which have been commanded; and at other times they lead to that which is evil, and so are joined to those matters which are prohibited. So this is a great asl that: “al-wasaa‘ilu lahaa ahkaamul-maqaasid (the means take on the same ruling as their aims).”
From this we learn that: “maa yatimmul-waajib illaa bihi fahuwa waajib (whatever is required to fulfill an obligation is itself an obligation).” Likewise, whatever is required to fufill a rmasnoon (recomendation) is itself recommened. Whatever leads to the establishment of a haraam (prohibition) is itself prohibited. And whatever leads to the establishment of a makrooh (detested act) is itself detested.
The full article may be read here:
http://salafipublications.com/sps/sp.cfm?subsecID=FQH01&articleID=FQH010001&pfriend=
