This study aims at exploring the lexical foundations attained in The Vocabulary Of The Qur'ān. The research comprises of an introduction, a preamble, three chapters and a conclusion. The introduction includes a presentation to the topic, the motives for choosing such a topic, along with the problem and the approach. The previous studies are also addressed. The preamble: The Vocabulary Of The Qur'ān, involves three sections. The first section discusses the author. The second section focuses on the general characteristics of the dictionary. The third section underlines the strange Quranic term, and its specificity with Ragheb Isfahani. It also underscores Ragheb Isfahani's works, reaching through them to what distinguishes his approach. The first chapter, fundamentals of the modern theoretical lexicography, sets up methodical remarks at the theoretical lexicography which will be applied on the dictionary. The chapter comprises of three sections: the first two sections discuss elements of the theoretical lexicography. While the third section discusses the specialized dictionary and its definition and characteristics. The second and third chapters represent the practical side of the theoretical lexicography applied on the dictionary: the second chapter, fundamentals of compiling The Vocabulary Of The Qur'ān, tackles the sources upon which the author relied to build up his dictionary. It also explains the linguistic levels of lexical entries. The third chapter, tackles the methodology by which the dictionary was compiled. In the conclusion, the study findings are highlighted with some recommendations