Terrorism is the systematic use of terror especially as a means of coercion.
In the present, there is no internationally agreed definition of terrorism.
Common definitions of terrorism refer only to those violent acts which are intended to create fear (terror), are perpetrated for an ideological goal as opposed to a lone attack, and combats.
Some definitions also include acts of unlawful violence and war.
The history of terrorist organizations suggests that they do not select terrorism for its political effectiveness. Individual terrorists tend to be motivated more by a desire for social solidarity with other members of their organization than by political platforms or strategic objectives, which are often murky and undefined.
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. A less politically and emotionally charged, and better defined, term (used not only for terrorists, and not including all those who have been described as terrorists) is violent non-state actor.