Fiqh, according to the Arabic language, means 'understanding'. We find this meaning used in the Qur'aan: "Take away the knot from the tongue, so that they would understand what I say". {Surah Taha, verses 27-28}
And according to Islamic law, the definition of 'Fiqh' is:
'Ma'rifah (knowing) the rulings of the Shariah (which are acted upon) from specific evidences.'
The meaning of our saying:
"...Ma'rifah..." is: certain knowledge as well as Dhann (meaning that when one things that what he has is correct but it doesn't reach the level of certainty). This is because knowledge of the rulings of fiqh can be with certainty or with Dhann as occurs in many of the issues in fiqh.
And the meaning of our saying:
"...Rulings of the Shariah..." means: The rulings that are taken from the Shariah, in terms of matters being compulsory or forbidden. What is outside of this is the rulings of the intellect like knowing that a whole is more than a fraction...
And the meaning of our statement:
"...Which are acted upon..." means that it has nothing to do with belief; rather, it refers to matters like Salaat, and Zakaat. Therefore what is outside of this is what is ascribed to beliefs: like belief in the oneness of Allah and knowledge of his names and attributes. According to the Islamic law terminology this is not called 'Fiqh'.
And the meaning of our saying:
"...from specific evidences." means that the evidences of fiqh, with the issues of fiqh, are specific. What leaves this definition is Usuul Ul Fiqh, because Usuul Ul Fiqh looks into the general evidences of fiqh (principles).
N.B: Some scholars have added to the end:
"...By the book and the Sunnah." Because of the fact that the sources of Fiqh should not come except from the Qur'an and the Authentic Sunnah. Or from the principles derived from the Qur'an and the Sunnah.