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In this article, we are to justify the variety in the word-order of Persian, Arabic and English in tile framework of the theoiy of Government and Binding and to show that this variety is partly due to such processes as “Topicalization” in English and “Scrambling” in Persian and Arabic. We have particularly emphasized the difference between these Iwo processes in that the former is related to configurational languages like English and the latter to flat languages like Persian and Arabic. On the basis of Saito’s proposal 1982, we have assumed that Persian and Arabic are flat in Phonetic Form and configurational in S-structure. Then on the basis of Berwick’s “Subset theoiy” 1982, we have assumed that D-sfructure in these languages are of an svo order and that S-structure can appear in an svo or/and soy order. As a result the variety in these languages results from two types of movement. One is NP movement, which is optionally applied in Phonetic Form and tile other is Head movement, which is obligatorily applied between D-structure and S-structure.