Abstrakt
The mathematical learning environment Bus is based on pupils' real-life experience and has been elaborated by M. Hejný to develop pupils' understanding of number as a state, an address, an operator of change and of comparison when it is grasped by the specific language of this environment.
The main result of our study is a description of the process in which individual 7-8 years old pupils lose their tendency to use irrelevant aspects of language and effectively select and structure those that are key in a given situation.