The word-formation system of Modern Turkic languages was formed in the result of a long period process of development. Its development history goes back to VI-VII centuries and takes its beginning from the Old Turkic written monuments. The Orhon written monuments are the oldest written records of the Old Turkic language, which survived to the present day. As a valuable heritage of shared historical period of all Turkic peoples, it needs new points on comparative methods of research by comparing Old Turkic language with modern Turkic languages in the connection with the history and worldview of Turkic people. The vocabulary stock of a language is unstable and it is enriched by means of borrowings and derivatives. There is quite a difference between word-stock of Old Turkic language and word-stock of modern Turkic languages. It was scientifically proved, that in the language of Old Turkic manuscripts there were both root words and derivatives. The types of derivatives in Orhon monuments are derived words, compound words and lexical-semantic variations. According to linguistic materials, in the language of Old Turkic monuments there were morphological, syntactic and semantic manners of derivation.