In this research, it is aimed to explore how students are able to define parallelogram and to establish relations with other quadrilaterals at each class level comparatively. Case study is chosen as the methodology of this study and the participants of the study are 120 middle school students from a state middle school in Turkey. Two open-ended questions are used to gather data and the descriptive analysis is used. The results of the study show that the students determine parallelogram based on its typical image. Furthermore, students have not fully grasp the hierarchical relation between these special quadrilaterals in their minds.