Abstract
The article discusses the definition of Rational Simile both as grammatical and rhetorical terminology. The researcher has tried to point out, within the idiomatic definition, the differences of opinions and interpretations among the grammatical and rhetorical scholars in the idiomatic definition of Rational Simile. The ancient rhetoric’s have cared a lot in their researches and works and have dealt with it in separate chapters and books. Imam Abd al-Qaher al-Jurjāni, was the first scholar how differentiate between Simile and Rational Simile in his book The Asrar ul Balāghā, then the rhetoric’s differed in its definition, the researcher mentioned the opinion of Imam Abd al-Qaher al-Jurjāni and the scholar AlSakaki, and al-Qazwinį, then he balanced among these definitions, and mentioned a comprehensive definition of Rational Simile which include all its kinds.