Abstract
The purpose of this study is to clarify the notion of "mathematizing" by Freudenthal. Freudenthal characterizes "mathematizing" by an activity as "organization". "Mathematizing" has not been enough interpreted from a viewpoint called as such an "organization" until now. Therefore, in this study, I define the notion of "mathematizing" based on the "re-invention" in the theory of mathematics education by Freudenthal. And I complement the notion of "mathematizing" by interpreting a meaning of "organization". In conclusion, "mathematizing" is an activity as act out a structure by working on reflective acting to organize experience.
