The reason of the repetition of the verses in the Holy Quran

Repetition can be studied from different dimensions such as the impact of repeated subject on the audience particularly in education. According to the famous proverb, "Lesson is once but repetition is a thousand", which is the experience of the nation practice and repetition is an important and essential principle to understand the matters much better. God(Allah) as the first teacher and trainer of man has applied the most paramount method in Quran which is an educative and humanizing book for human beings to be noted and return towards him. “And certainly we have repeated (warnings) in this Quran that they may be mindful” (isra ,41), “and we have diversified the signs (or verses) that they might return”.(Alahqaf,27)
Researchers of Quran have divided the repetition in Quran into two parts: literal and virtual repetition. In this paper the view of Quran researchers and interpreters relating to the occurrence of repetition - both literal and virtual - have been studied, and for this purpose the overall reasons of the problem have been planned briefly, and then the viewpoints related to all repeated verses have been studied one by one.