International relations is an interdisciplinary field that studies the interactions between nation-states and non-governmental organizations in areas such as politics, economics, and security. It is a major subdiscipline of political science, along with comparative politics, political theory, political methodology, and public administration. The study of international relations involves theoretical approaches based on solid evidence, and the two major theories of international relations are realism and liberalism.

International relations is a complex field that covers a broad range of topics, including human rights, global poverty, the environment, economics, globalization, security, global ethics, and the political environment. It is not limited to the study of nation-states and their interactions, but also includes non-state actors, international political economy, international security, international environment, globalization, terrorism, area studies, and military studies.

The subject matter of international relations is not limited to political science, but also draws heavily from other fields such as anthropology, economics, geography, law, philosophy, sociology, and history. The study of international relations is interdisciplinary in nature, blending the fields of economics, history, and political science.

In summary, the core subject of international relations as an academic discipline is the study of the interactions between nation-states and non-governmental organizations in areas such as politics, economics, and security, and it covers a broad range of topics that are not limited to political science but also draw from other fields such as anthropology, economics, geography, law, philosophy, sociology, and history.