<em>The purpose of the</em> research<em> in the study was to study the development of learning discovery-based pocket book media on students' mathematical understanding abilities. The research methodology used is the method of research and development (R &amp; D). Based on the results of development, research, and discussion, it can be concluded that the development of learning discovery-based pocket book media on mathematical understanding skills reaches a level of validity with excellent categories and achieves practicality with very practical criteria</em>