Résumé
TWG04 on geometrical thinking had more than 22 participants from 10 countries. During the sessions, the participants discussed thirteen papers and three posters (one paper and two posters were submitted but not discussed in the working group). TWG04 about geometrical thinking has been working on this topic for many CERME sessions, and mostly studied what geometrical thinking would mean. It is concerned with research and development of geometrical thinking from pre-school up to University teaching and learning, including any type of geometry. In line with the previous sessions, CERME8 tried to identify four competencies that helped describe geometrical thinking: reasoning, figural, operational and visual (Maschietto et al., 2013). The discussion paper focused on educational aspects related to the development of these geometrical competencies for students, the
difficulties of learning and the design of curricula and their implementation. These four poles were very helpful to use a common language and shared reference concepts. They also allowed to show how the many faces of geometrical activity are intertwined, which made necessary a clarification of what was meant by these poles.