چكيده فارسي :
This paper deals with the vowel system in Iraqi Arabic and in Classical and Modern Standard Arabic. It shows within the framework of the optimality theory the indispensability of the vowel system for theClassical and Modern Standard Arabic. This indispensability results from the multifunctionality of the Case system in these two variants of Arabic. In Case of the Classical and Modern Standard Arabic, the optimality theory has its own means to keep this vowel system unaltered in the output. The best way to be faithful to this vowel system is to put the faithfulness constraint of the optimality theory on the very left edge of the constraint hierarchy; this procedure ensures then that the output and the input will be identical. In contrast to Classical and Modern Standard Arabic, Iraqi Arabic does not exhibit case affixes on nominal phrases, therefore the ranking of the constraints hierarchy will look very different from that of Classical and Modern Standard Arabic. This dysfunctionality of the vowel system for the Iraqi Arabic can be shown by the lower-ranking of the faithfulness constrains on the hierarchy. As a result, vowel affixes must be syncopated.
