Huge collection of diverse written knowledge and effort of the politicians, linguists, novelists, poets, anthropologists, folk historians, sociologists, and tourists are in the area of oriental studies. Most postcolonial thinkers like Edward Said review all of these efforts as Orientalism discourse. This article focused on the question that which aspects and features persuaded postـcolonial thinkers to equate this diverse collection and placed them under one title. By helping from postـcolonial thinkers; eleven common features can be counted for this series of studies, which include: Linking with power, East invention, generalization and integration, and archival nature and historicism, duality of good and bad, differentiation between "us" and "them", thinking instead of the other, selfـcentered, centrality of western needs, our supremacy and the other Inferiority. These common features incline postـcolonial scholars to place this plural collection under the title of orientalism; so it`s the greatest example of Interdisciplinary studies.