Numerous terms used in the context of Old Turkish texts, especially in the language of Old Uyghur official-legal documents and civil documents, indicate that the Turkish legal language has an ancient history. The texts formed in different alphabets, writing systems and various environments during the Uyghur Khaganate and later periods are valuable sources that shed light on the history of our language. Although these texts have always been at the center of attention of researchers, the language of legal documents, official documents, the vocabulary of texts with legal and official meanings, the ways of derivation of words have not been studied extensively and comprehensively. The researches were mostly carried out in the context of syntax or thematic regions, and the language composition of the language of the documents was not evaluated according to its lexical-semantic, morphological structure and origin. The naming and derivation ways of legal concepts and understandings regarding the official-business style, the nomenclature and processes of words belonging to general usage should be put forward in the context of the texts, and the issues of forming terms through the language's own means or quotations should be examined in the light of historical facts. Vocabulary of Old Turkish Texts reveals that legal terms are derived in two ways: the language's own possibilities and quotations. Considering the structure and grammatical rules of Turkish, we can classify legal terms as a) semantic, b) morphological, c) syntactic, d) kalka, e) abbreviation of words. These derivational ways, which have different functionality in various periods, are also followed in the language of official-legal documents in old Uyghur language. In this paper, in the light of old Turkish legal documents, the terminology is discussed in a semantic way, in this method, which is one of the most efficient and first ways of word derivation, the position of polysemy (polysemy), the transition of words from general use to specific use - term by changing their meaning, the semantic expansion of the word are examined. manifestations have been studied. Key words: Old Turkish, Official-business style, Law, Terminology, Word derivation, Semantics