ILMU ‘L-USUL علم الاصول
The science of the “roots”, or fundamentals of the religion of Muhammad, namely, of the Qur’an, Ahadis, Ijma’, and Qiyas. The science of exegesis, or the rules of interpretation of these four roots of Islam. An explanation of the methods of this science will be found in the article on the QUR’AN, Sect. Viii., the same principles applying to the other three fundamentals.
The best know works on the “Ilmu ‘l-Usu are the Manar, by ‘Abdu ‘llah ibn Ahmad an-Nasafi, A.H. 719, and its commentary, the Nuru ‘l-Anwar; also at-Tanqih, by ‘Ubaidu ‘llah ibn Mas’ud, A.H. 747, with its commentary, at-Tauzih, by the same author, and a super-commentary, the Talwihu ‘t-Tauzih, by Sa’du ‘d-din Mas’ud ibn ‘Umar at-Taftazani, A.D. 792.
Based on Hughes, Dictionary of Islam