This research aims to reveal the problem of the mother of This paper aims at revealing the problem of () of Ingratitude; This is because it carries more than one meaning, such as reasoning, negation, and affirmation. Stemming from here , several questions present themselves: is the () for negating or confirming? Why was it called the () of ingratitude? Why did not we call it the () of negation? If it were for negation, the sentence would have been confirmed. That is because the negation of the negation is simply affirmation, and consequently the meaning of the sentence is distorted. In addition to disagreeing over its function by the grammarians , the Basrians said that it is not subjunctive in itself, but the function is for () it is supposed to be present, and the Kufics said that it is subjunctive by itself. The paper dealt with an application aspect on the use of () of Ingratitude in the Holy Quran and its implications The paper included many sections, including: the ingratitude on the part of the linguistic meaning and the idiomatic meaning, the problem of naming () of Ingratitude, or the () of the negation), the issue of negation, affirmation and reasoning with the () of ingratitude, the difference between the () which is similar to () and the () of ingratitude, the dispute over the work of () ingratitude and the problem of showing the infinitive ( ), the relation between the () of the ingratitude and (), the removal of the ()of the ingratitude, and whether to explicitly show the infinitive () or not. All of these sections, the paper tried through them to answer a number of questions that come to mind about the () of ingratitude and the problems related to it.