The paper focuses on the issue of how the terminology which a person is able to use actively influences her perception of pedagogical reality. The research is conducted within the frame of the international Lexicon Project.
In the paper, the process of evolution of Czech lexicon of didactical terms for description of facts from educational reality is described. The methodology and materials used for creation of the lexicon are presented.
The main methodological approach used is open and axial coding of episodes from classroom video recordings. The paper answers the following research question: What is the structure of terms suitable for description of a lesson of mathematics?