摘要：The purpose of this study was to investigate how pre-service elementary mathematics teachers explain the concepts of point, line and plane, which are primitive terms of Euclidean geometry. A qualitative exploratory case study design was conducted with 61 pre-service mathematics teachers who were selected by the criterion sampling method. As a data collection tool, an open-ended questionnaire was used to determine how prospective teachers can explain point, line and plane concepts in the classroom environment where they will be teaching, and their explanations were taken in writing. The data analysis was done using content analysis technique by means of NVivo10. The findings showed that pre-service mathematics teachers tended to use some signs related to the characteristics of three primitive terms: point, line and plane they attempted to explain as well as the signs belonging to their essence. This can be due to the fact that the concepts tried to be explained are primitive terms and that the explanations given by Euclid about these terms are not easy to understand at the secondary level. Moreover, in some explanations, it was found that more than one sign was used by focusing on the features, models and symbols of the related concept to make the definition more understandable. On the other hand, considering the explanations made by the pre-service teachers in this study, it should be remembered that although the signs (model, shape, feature, symbol, etc.) used for the concept seem to constitute its definition, these signs cannot always literally represent the concept they try to explain and cannot be used in place of the that concept.
