Outstanding for its tajdid or reform, Muhammadiyah is associated to several terms similar to the reform movement (tajdidfi ’l-Islam) such as the revival of Islam (al-shahwa al-Islamy, al-ba’ath al-Islamy). Deliar Noer, James L. Peacock, William Shepard and some scholars categorize Muhammadiyah as the Islamic modernism. Alfi e and Wertheim classify it into the Islamic reformism. Abubakar Atjeh calls it a movement back to the Salaf (Muhyi Atsari al-Salaf). Clifford Geertz, George Kahin, Robert van Neil, and others, incorporate Muhammadiyah into the socio-cultural movement. The substance or content of these predicates although expressed in a variety of terms could be defi ned as the reform movement or tajdid. Basically, the nature of Muhammadiyah is tajdid or the reform movement.