What is the Mufassal in the Holy Qur’aan? Who called it that and why was it called that?.?

As you can very well see, the subject of Muffassal is clearly undefined and is actually left to the individual as to which suras constitute Muffassal. In the case of leading prayers, the Imam should decide what is best for his congregation and to vary the recitation of the suras to accommodate for the members.