Аннотация: Mason and Spence’s (1999) work demonstrate a detailed view into the concept of knowing. Although they highlight the importance of not-knowing as a first step, it is a topic that is not well researched. This study aims at expanding that research, by analyzing not-knowing expressions from teacher to student and possible connections to be found. During a course of geometric reasoning student teachers were asked to reason with a tangram while simultaneously recording their expressions of not-knowing and reflecting on it periodically. Student teachers were then tasked to teach this lesson to their students, who would also reflect and express their forms of not-knowing. Findings presented no real link between teacher-student expressions of not-knowing, but two major conclusions were made. Individuals altogether struggle conveying their not-knowing clearly and when they did express it, these expressions leaned heavily on not-knowing-that and not-knowing-how forms. A discussion follows to interpret said findings. A conclusion is made detailing key points in the study and what comes next for the concept of not-knowing.