Introduction -- Part 1. Theoretical approaches: realisms; liberalisms; game theory; constructivisms; peace studies; critical theory; feminisms; international political sociology -- Part 2. key concepts: uncertainty; polarity; culture; war; coercion; terrorism; intelligence; genocide and crimes against humanity; ethnic conflict; human security poverty; climate change and environmental security; health -- Part 3. Institutions: alliances; regional institutions; the united nations; peace operations; the nuclear disarmament and non-proliferation regime; private security companies -- Part 4. Contemporary challenges: international arms trade; counterterrorism; counterinsurgency; the responsibility to protect; transnational organized crime; population movements; energy security -- Part 5. Conclusions: the academic and policy worlds; what future for security studies?.