Terrorism is, most simply, policy intended to intimidate or cause terror. It is more commonly understood as an act which (1) is intended to create fear (terror), (2) is perpetrated for an ideological goal (as opposed to a materialistic goal or a lone attack), and (3) deliberately targets (or disregards the safety of) non-combatants. Some definitions also include acts of unlawful violence or unconventional warfare, but at present, there is no internationally agreed upon definition of terrorism.

A person who practices terrorism is a terrorist. Acts of terrorism are criminal acts according to United Nations Security Council Resolution 1373 and the domestic jurisprudence of almost all nations.

The word “terrorism” is politically and emotionally charged,Hoffman, Bruce "Inside Terrorism" Columbia University Press 1998 ISBN 0-231-11468-0. Page 32. See review in The New York TimesInside Terrorism and this greatly compounds the difficulty of providing a precise definition. A 1988 study by the United States Army found that over 100 definitions of the word “terrorism” have been used.Dr. Jeffrey Record, Bounding the Global War on Terrorism(PDF) The concept of terrorism is itself controversial because it is often used by states to delegitimize political or foreign opponents, and potentially legitimize the state's own use of terror against them.

The history of terrorist organizations suggests that they do not practice terrorism only for its political effectiveness; individual terrorists are also motivated by a desire for social solidarity with other members.

Terrorism has been practiced by a broad array of political organizations for furthering their objectives. It has been practiced by both right-wing and left-wing political parties, nationalistic groups, religious groups, revolutionaries, and ruling governments.

Origin of term

main: Definition of terrorism

"Terror" comes from a Latin word meaning "to frighten". The terror cimbricus was a panic and state of emergency in Rome in response to the approach of warriors of the Cimbri tribe in 105BC. The Jacobins cited this precedent when imposing a Reign of Terror during the French Revolution. After the Jacobins lost power, the word "terrorist" became a term of abuse. Although the Reign of Terror was imposed by a government, in modern times "terrorism" usually refers to the killing of innocent people by a private group in such a way as to create a media spectacle. This meaning can be traced back to Sergey Nechayev, who described himself as a "terrorist".Crenshaw, Martha, Terrorism in Context, p. 77. Nechayev founded the Russian terrorist group "People's Retribution" (Народная расправа) in 1869.