In this assay I have studied the structure of izlak which took place in disciplines that interested in Arabic phonetics in some way. The structure of izlak, in many field related to phonetics, has been used to express one of the conditions made by the organs during the process of producing speak sounds. But this structure didn't mentioned in the earliest sources and in some of the latests. On the other hand we have noticed that the explanations of izlak term in the earliest works and the latest works of tacwid were different, and also that the new explanation was getting widely accepted. To follow this structure, which it's all definitions were connected with its root meaning, we reviewed classical dictionaries, works concerned with Arabic language, tacwid works and other sources. The study has pointed out that although izlak is an affecting characteristic which influences the sound interactions, it is basically not an articulation subject.