Following an axiomatical way the Teacher, the Student, a Language L of verbal communications and a Text-book T of some mathematical branch have been introduced. Seven axioms concerning these elements and the Learning process have been assumed. Then using suitable Graphs the Lexical, Logical and Didactical structures of T and four gauge for the difficulties connected with the Student’s Learning process have been defined. Four abstraction classes for theorems and 4g + 1 classes of Learning level have been stated. Here g equals the numbeer of maximal elements of the Graph which defines the Didactical structure of T, and it is related to some complexity Classes of Exercises. On the other hand some fundamental Rules to develop abilities in Inductive Reasoning have been stated. (orig.)