Abstract
Arab linguists after the processes of compiling the language-specific uses of the Arabs and reaching the language rules from the compiled data entered into in-depth discussions about language rules. Linguists, who initially focused on basic language issues over time they have come to the level of making more detailed explanations on the subjects. While they focused on primary and compulsory information in the first stages, they later focused on the background of compulsory and basic information in parallel with the developments in both linguistics and other sciences. With the completion of the conceptual framework of Naḥw, they discussed language issues in more depth over concepts and produced thoughts on the reasons behind the language rules and directly affecting the language rule. In this framework, the concept of “cause” emerged. However, linguists were not satisfied with the explanation of the primary reasons related to language rules, and they took the search for reasons to an advanced level. During “cause” (‘ille)-based studies one of the phenomena that is effective in the background of syntax rules and draws attention in the explanations of linguists has been the phenomenon of similarity. Under normal circumstances, an element that is not effective in terms of grammar has become effective on other elements owing to the phenomenon of similarity. In this study, the phenomenon of similarity as a cause will be discussed in the context of the essential and the detail.