International relations (IR) or international affairs, depending on academic institution, is either a field of political science, an interdisciplinary academic field similar to global studies, or an entirely independent academic discipline in which students take a variety of internationally focused courses in social science and humanities disciplines. In both cases, the field studies relationships between political entities (polities) such as states, sovereign states, empires, inter-governmental organizations(IGOs), international non-governmental organizations (INs), non-governmental organizations (NGOs), and multinational corporations (MNCs), and the wider world-systems produced by this interaction. International relations is an academic and a public policy field, and so can be positive and normative, because it analyzes and formulates the foreign policy of a given State.
As political activity, international relations dates from the time of the Greek historian Thucydides (c. 460–395 BC), and, in the early 20th century, became a discrete academic field (No. 5901 in the 4-digit UNESCO Nomenclature) within political science. In practice International Relations and International Affairs forms a separate academic program or field from Political Science, and the courses taught therein are highly interdisciplinary.