"An" is one of the letters of Jar, which is generally interpreted, "mojawazah" by syntacticians; But they do not mention the exact meaning of "mojawazah" and only explain "mojawazah" through some examples. Also, they mention many other meanings for "an" that have no relation between them. This paper has tried to find a single meaning for "an" in a descriptive-analytical method based on the theory of the principle of meaning and reasoning and citing the use of "an" in the verses of the Qur'an so that all uses of "an" in the Qur'an and general non-common uses. This is an attempt to analyze it in Arabic accurately and acceptably based on this main meaning. From this article, it was obtained: The meaning of "an" in the Qur'an is the same meaning everywhere that syntacticians interpret it as "mojawazah". "Mojawazah" means the permanence of the dimension and the preservation of distance, and a kind of ambiguity must be taken into account; therefore, in principle, one should not understand the meaning of beginning from "an" and the use of "Men" instead of "An" is not correct. What sometimes makes "An" resemble "Men" is the meaning of mediation, which is the result of the dimension and ambiguity used by "mojawazah". Also, none of the expressive meanings of syntacticians and commentators were used to use "an" instead of other letters, and the analysis of "an" in all these examples with a synonymous meaning was easier and more accurate.