This chapter analyses the worldwide terminologies to indicate the sub-sector within which civil society organizations broadly exist. From the analysis of the international literature, there is a significant variety of terminological statements, among which we have selected ten that represent paradigmatic examples of the bi-directional link between the conceptual definition of a phenomenon and the socio-cultural context of reference. These are: (1) nonprofit sector; (2) charitable sector; (3) philanthropic sector; (4) informal sector; (5) third sector; (6) independent sector; (7) voluntary sector; (8) private nongovernmental sector; (9) social economics; (10) intermediary system and private initiative.