The First treats the study of "Kashshaf istilāhāt al funūn and specialised Lexicon Includes four secondary chapters. The First deals with Tehanoy's Translation. I tried to investigate closely. The Seconds Discusses "Kashshaf istilahat al funun" where the inducements that pushed Tehanoy for his authorship and his description of five impressions of Lexicon is discussed. Then, I depended on statistics for placement of Arts Terminologies Lexicon in a suitable place between other specialised Lexicons or Encyclopedian Lexicons. The third deals contrapuntal lexicon studying. I also showed concern with the secondary chapter for the terminology studying, and I defined it in language and term. I gave a brief relation of its conception and its importance. The Second Chapter discusses the plural methodizing and its applications with "Kashshaf iştilahāt al funūn" through three discussions. The first discussion is concerned with the sources study of Tehanoy Lexicon where theres is a discussion explained for the approach that is related by Tehanoy and his sources. I also attached an appendix that previews Terminologies Explorer sources according to science that Tehanoy employed. I studied them through two levels; where first level of entrances, and second level of definitions sentences&explanations. I ended the chapter with Tehanoy's position in facing foreign languages. The third discusses deals whith the depended displays types that Tehanoy had. The third Chapter of research discusses a methodical setting and its appliances of " Kashshaf istilāhāt al funun". Also, through three discussions, this research partook of other subjects, where First Discussion that studied types of Lexicon entrances. Second discussion is concerned with the mentioned definitions of Kashshaf istilahat al funun". These definitions are divided as the following: a) basic definitions that deal with a sonic definition, b) Logical definition, c) Identification with illustration, d) Identification with elucidative examples and context ....ect. I also showed concern with the other section of "Assistance Definitions" that Tehanoy depended on them for the clarification of his terminologies definitions. Finally, I ended my thesis with the important achieved results with sources and references that I depended on , and an index that clarifies the thesis contents