This thesis starts up from a question raised by the old applications to the concept of Saja'a (Assonance): Saja'a has third section beside to duality of poetry and prose? There is a different view of Saja's that it is not only rhetorical device to perform the refinement of the articulation in the speech , but it also has a structure of its constituent elements and rules . But in return, does the Saja'a have rhyme elements of a clear quality make it an independent type of speech? Accordingly, the purpose of this study is a comprehensive and accurate review of the concept of Saja'a and to analyze the debate around it in criticism of heritage as, then I followed up the stages of using Saja'a in consecutive ages of the Arabic Literature. As well as monitor the aspects of developments in its concept and structure. The study focused on the disclosure about the features of the qualitative character of Saja'a that may qualify it to be an independent gender based on comparable poetry and prose and the situation of the old critics of this comparison, as well as the views of modern scholars who have studied the characteristics of rhyme and rhetorical structure outside the framework of care. The study found there is something of a mystery in the prevailing concept of Saja'a , that in the past, Saja'a had a broader concept and it is cleared by the way of their dealing with Saja'a (Assonance), as well it is proved in the modern researches that have shown that Saja'a structure is characterized by systemic structure and specified rhythmic systems. And that would reinforce the concept of the quality Saja'a and make it an articulation of rhetorical device because this concept raises doubt about the situation of rhetoricians of Saja'a. We tried in this study tried to find to how extent this type through the procedural analysis through formal structure and rhythmic structure.