This article notes the systemic lack of conceptual clarity in the social sciences and attempts to illustrate the adverse consequences by closer examination of the particular example of the interest group field. It indicates the significant ambiguities implicit in the term. Not all policy-influencing organisations are interest groups as normally understood, but because there is a lack of an appropriate label the term interest group is used by default. The article seeks to distinguish between interest groups and other policy relevant bodies—often corporations or institutions. It finds disadvantages in adopting a functional interpretation of the interest group term (i.e. any organisation trying to influence public policy). While the wider range of organisations are crucial in understanding the making of public policy, it is confusing to assume that this wider population are all interest groups. The article instead advances the complementary notions of pressure participant, policy participant and interest group. This slightly expanded repertoire of terms avoids conflating important distinctions, and, in Sartori's term permits ‘disambiguation’. The core assumption is that the search for comparative data and exploration of normative questions implies some harmonisation in the interest group currency.