The Arabic word fiqh means knowledge, understanding and comprehension. It refers to the legal rulings of the Muslim scholars, based on their knowledge of the shari`ah; and as such is the third source of rulings. The science of fiqh started in the second century after Hijrah, when the Islamic state expanded and faced several issues which were not explicitly covered in the Qur'an and Sunnah of the Prophet (saas). Rulings based on the unanimity of Muslim scholars and direct analogy are binding. The four Sunni schools of thought, Hanafi, Maliki, Shafi'i and Hanbali, are identical in approximately 75% of their legal conclusions. Variances in the remaining questions are traceable to methodological differences in understanding or authentication of the primary textual evidence. Differing viewpoints sometimes exist even within a single school of thought.