A central problem with social science concepts is the process in which a theoretical concept gets translated into a more concrete element, and after that, an empirically valid concept. Because of the abstract nature of theoretical concepts there needs to be clear definitions of a concept. At least to the extent that the concept intends to explain empirical phenomena. In this paper the concepts of social marginalization, social exclusion and social alienation will be investigated with the theoretical assumption that a concept can be divided into (1) a basic theoretical element, (2) a constitutive element and (3) an operational indicator. After a review of different versions of the concepts in question, the paper examines the commonalities and differences between the concepts. As the concepts differ, the theoretical structure differs. After an analysis of the different concepts, the paper formulates a series of central commonalities and differences among the concepts. The first dimension has to do with the difference between an individual and structural viewpoint of the concepts. The individual aspects can in turn be divided into material and psychological aspects of the concept. The structures can be divided into economic, social and political dimensions. Another central point of the paper has to do with the absence of a clear boundary between what is necessarily a part of the concept and what is not. If A and B are apart och the more abstract concept C, there needs to be a clear statement about the question if C can still exist if only A or B exist. The alternative definitional path is to state that C exist only in circumstances when A and B exist simultaneously.