Case assigner is a central issue in Arabic grammar, which has been a concern in The factor issue is one of the most eminent cases in Arabic grammar, and it was taken care of in grammatical thought, both ancient and modern, and the impact was obviously noticed in the large number of grammatical disagreements, the arrangement of chapters, and the topics. And whoever notices the theoretical factor in what some of the grammarians have quoted will realize differences between the theoretical side and the practical side of this factor. This has caused multiple interpretations among the grammarians, and this was attributed to Sibawayh, Ibn Jinni, and Al-Radi. All of these have prompted me to conduct this research. Therefore, in this research, I employed the descriptive approach as a method, and utilized the tools of induction and analysis. I achieved the goals of dealing with the topic in four dimensions (chapters) and a conclusion. The first dimension includes literary definitions of the factor in grammar. And the second dimension processes the factor as grammatical terminology. The third dimension discusses the emergence of the idea of the factor. And the last dimension explains the grammarians disagreement in refering the factor performance to words and meanings between theoretical and practical speech. Furthermore, the research reached some conclusions, many of which contain the most prominent findings of the research, including: the factor theory was not by any means the result of creative thought among the ancient scholars who initiated it, but rather the result of extrapolation and analysis of language texts. In addition to that both ancient and modern grammarians were unable to develop an alternative system for the idea of the factor. And that the speaker is not the factor in the applied grammar thoughts. Finally, the relationship between the speaker and the factors is selection and employment.