The term "Ummi" which is used in Quran and Islamic narratives carries a special meaning in each case. The Holy Prophet has been described as "Ummi" twice in the Holy Quran. The scholars in terminology and interpretation define "Ummi" as a person who cannot read and write, therefore, they believe the Holy Prophet, like all the ordinary people in the Arab world, did not know how to read and write. In the first part of the present article, we initially present a definition of the term from the lexical books, and then study this fact in Quranic verses and in different interpretations. In the third part, the controversies in the book Basair al-darajat(which claims that The Prophet could read and write in 72 or 73 languages) with Quranic verse are studied. The article tries to collect all the narrative stories and verses and then choose the concluding remarks, and in the end, historical and narrative reasons and evidence proving prophets being Ummi is presented.