The aim of the research presented in this paper is to propose a classification of the manifestation of uncertainty to offer a basis for a shared understanding and characterization of the concept of uncertainty within the area of design research. During the past decade a growing number of papers about uncertainty have been published. These papers focus on different aspects and points of the design process and offer insights on different aspects of uncertainty. The research presented in this paper describes the manifestation of uncertainty and proposes a classification. The classification consists of context uncertainty arising from the situation circumstances, data uncertainty stemming from input information or data into a further process, model uncertainty resulting from the simplifications in models, and phenomenological uncertainty connected to the outcome of a process. Each of these categories is described in detail offering a basis for positioning specific research contributions published in previous ICED conferences. This offers a basis for the consideration of the appropriate uncertainty management methods