Terrorism is broadly defined as the use of violence by a non-state actor to pursue a political end or to intimidate civilians. Although there is no universally recognized definition for terrorism as codified through international law, national and international agencies employ workable understandings of terrorism to cooperate meaningfully on counterterrorism efforts.

U.N. Member States have not reached a consensus on the definition of terrorism. Nonetheless, several U.N. treaties—including the International Convention for the Suppression of the Financing of Terrorism (1999) and Security Council Resolution 1566 (2004)—provide a catalog of terrorist acts and establish that states have an obligation to prosecute or extradite the perpetrators. The U.N. Security Council meanwhile requires Member States to take actions to counter terrorist groups ISIS and al-Qaeda, as well as their affiliated groups, entities, and individuals.

While the United Nations has not settled on a definition of terrorism, some international bodies have managed to reach a consensus. The European Union, for example, has defined terrorist acts as those committed with the aim of “seriously intimidating a population,” “unduly compelling a government or international organisation to perform or abstain from performing any act,” or “seriously destabilising or destroying the fundamental political, constitutional, economic or social structures of a country or an international organisation.”

Governments define terrorism on a national level through their respective criminal codes and legislation. Within in the United States, definitions may even vary by body or agency. The U.S. Criminal Code, for example, defines terrorism as “premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents, usually intended to influence an audience.” The Federal Bureau of Investigation (FBI) employs a slightly different definition of terrorism, calling it “the unlawful use of force or violence against persons or property to intimidate or coerce a government, the civilian population, or any segment thereof, in furtherance of political or social objectives.”

Although definitions of terrorism may vary between agencies and governments, shared characteristics between definitions of terrorism have allowed for inter-organizational cooperation at the national, regional, and international levels. Commonalities between definitions and objectives have allowed international bodies to work collaboratively to counter al-Qaeda and ISIS, among other international terrorist organizations.

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Daily Dose

Extremists: Their Words. Their Actions.


On May 8, 2019, Taliban insurgents detonated an explosive-laden vehicle and then broke into American NGO Counterpart International’s offices in Kabul. At least seven people were killed and 24 were injured.

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