This article surveys the history of the concept of democracy from Ancient times to the present. According to the author, the conceptual history of democracy shows that the overwhelming success of the concept is most of all due to its ability to subsume very different historical ideas and realities under its semantic field. Moreover, the historical evolution of the concept reveals that no unequivocal definition is possible because of the significant paradoxes, aporias, and contradictions it contains. These are popular sovereignty vs. representation, quality vs. quantity, liberty vs. equality, individual vs. collective, and, finally, the synchronicity between similarities and dissimilarities. The ubiquitous usage of democracy in present-day political language makes it impossible to speak of it from an external perspective. Thus, both democratic theory and practice are suffused with empirical and normative elements.