Ferdinand Tönnies's oeuvre Gemeinschaft und Gesellschaft, published in 1887, has been seminal for the social and human sciences in general, and is no less interesting for intellectual historians and theoreticians of concept formation in particular. Tönnies subscribed to the belief that terms could be rendered less ambiguous, defining the words Gemeinschaft and Gesellschaft more narrowly than their contemporary usage. In so doing, he sought to reconcile a heterogeneous agenda initially consisting in offering a diagnosis of vast historical developments and later consisting in providing heuristic tools to analyze individual relationships. This article examines the origins of the concepts and their politicized transformation prior to and subsequent to the publication of his work. As such, it takes on the transformation of Gemeinschaft during the romantic era and its revival by Germany's nationalist right wing and contrasts it with its appropriation by left-leaning communitarian movements in the English-speaking world. The polysemy of the terms in the German language accounts for their semantic evolution, for amalgamations of meanings within Tönnies's conceptual system, and for conundrums in translating the work into English or French. Although the terms were erroneously supposed to have been immediately applicable as ideal types, their adaptation, inter alia by Max Weber or by Talcott Parsons in the form of pattern variables, has been important in the reception of Tönnies's work in the social sciences.