International relations (IR) or international affairs (IA) — commonly also referred to as international studies (IS), global studies (GS), or global affairs (GA) — is the study of interconnectedness of politics, economics and law on a global level. Depending on the academic institution, it 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 all cases, the field studies relationships between political entities (polities) such as sovereign states, inter-governmental organizations (IGOs), international non-governmental organizations (INGOs), other 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 analyses 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.