"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".Nechayev founded the Russian terrorist group "People's Retribution" (Народная расправа) in 1869.

In November 2004, a United Nations Security Council report described terrorism as any act "intended to cause death or serious bodily harm to civilians or non-combatants with the purpose of intimidating a population or compelling a government or an international organization to do or abstain from doing any act". (Note that this report does not constitute international law).

In many countries, acts of terrorism are legally distinguished from criminal acts done for other purposes, and "terrorism" is defined by statute; see definition of terrorism for particular definitions. Common principles among legal definitions of terrorism provide an emerging consensus as to meaning and also foster cooperation between law enforcement personnel in different countries. Among these definitions there are several that do not recognize the possibility of legitimate use of violence by civilians against an invader in an occupied country and would, thus label all resistance movements as terrorist groups. Others make a distinction between lawful and unlawful use of violence. Ultimately, the distinction is a political judgment.

Official definitions determine counter-terrorism policy, and are often developed to serve it. Most government definitions outline the following key criteria: target, objective, motive, perpetrator, and legitimacy or legality of the act. Terrorism is also often recognizable by a following statement from the perpetrators.

Violence – According to Walter Laqueur of the Center for Strategic and International Studies, "the only general characteristic of terrorism generally agreed upon is that terrorism involves violence and the threat of violence". However, the criterion of violence alone does not produce a useful definition, as it includes many acts not usually considered terrorism: war, riot, organized crime, or even a simple assault. Property destruction that does not endanger life is not usually considered a violent crime, but some have described property destruction by the Earth Liberation Front and Animal Liberation Front as violence and terrorism; see eco-terrorism.

Psychological impact and fear – The attack was carried out in such a way as to maximize the severity and length of the psychological impact. Each act of terrorism is a “performance” devised to have an impact on many large audiences. Terrorists also attack national symbols, to show power and to attempt to shake the foundation of the country or society they are opposed to. This may negatively affect a government, while increasing the prestige of the given terrorist organization and/or ideology behind a terrorist act.

Perpetrated for a political goal – Something that many acts of terrorism have in common is a political purpose. Terrorism is a political tactic, like letter-writing or protesting, which is used by activists when they believe that no other means will effect the kind of change they desire. The change is desired so badly that failure to achieve change is seen as a worse outcome than the deaths of civilians. This is often where the inter-relationship between terrorism and religion occurs. When a political struggle is integrated into the framework of a religious or "cosmic"struggle, such as over the control of an ancestral homeland or holy site such as Israel and Jerusalem, failing in the political goal (nationalism) becomes equated with spiritual failure, which, for the highly committed, is worse than their own death or the deaths of innocent civilians. One definition that that combines the key elements was developed at the George C. Marshall Center for European Security Studies by Carsten Bockstette: "Terrorism is defined as political violence in an asymmetrical conflict that is designed to induce terror and psychic fear (sometimes indiscriminate) through the violent victimization and destruction of noncombatant targets (sometimes iconic symbols). Such acts are meant to send a message from an illicit clandestine organization. The purpose of terrorism is to exploit the media in order to achieve maximum attainable publicity as an amplifying force multiplier in order to influence the targeted audience(s) in order to reach short- and midterm political goals and/or desired long-term end states."

Deliberate targeting of non-combatants – It is commonly held that the distinctive nature of terrorism lies in its intentional and specific selection of civilians as direct targets. Specifically, the criminal intent is shown when babies, children, mothers and the elderly are murdered, or injured and put in harm's way. Much of the time, the victims of terrorism are targeted not because they are threats, but because they are specific "symbols, tools, animals or corrupt beings" that tie into a specific view of the world that the terrorists possess. Their suffering accomplishes the terrorists' goals of instilling fear, getting their message out to an audience or otherwise satisfying the demands of their often radical religious and political agendas.

Unlawfulness or illegitimacy – Some official (notably government) definitions of terrorism add a criterion of illegitimacy or unlawfulness to distinguish between actions authorized by a government (and thus "lawful") and those of other actors, including individuals and small groups. Using this criterion, actions that would otherwise qualify as terrorism would not be considered terrorism if they were government sanctioned. For example, firebombing a city, which is designed to affect civilian support for a cause, would not be considered terrorism if it were authorized by a government. This criterion is inherently problematic and is not universally accepted, because: it denies the existence of state terrorism; the same act may or may not be classed as terrorism depending on whether its sponsorship is traced to a "legitimate" government; "legitimacy" and "lawfulness" are subjective, depending on the perspective of one government or another; and it diverges from the historically accepted meaning and origin of the term.For these reasons, this criterion is not universally accepted; most dictionary definitions of the term do not include this criterion.

The terms "terrorism" and "terrorist" (someone who engages in terrorism) carry strong negative connotations. These terms are often used as political labels, to condemn violence or the threat of violence by certain actors as immoral, indiscriminate, unjustified or to condemn an entire segment of a population.Those labelled "terrorists" rarely identify themselves as such, and typically use other terms or terms specific to their situation, such as separatist, freedom fighter, liberator, revolutionary, vigilante, militant, paramilitary, guerrilla, rebel or any similar-meaning word in other languages and cultures. Jihadi, mujaheddin, and fedayeen are similar Arabic words which have entered the English lexicon.

On the question of whether particular terrorist acts, such as murder, can be justified as the lesser evil in a particular circumstance, philosophers have expressed different views: while, according to David Rodin, utilitarian philosophers can (in theory) conceive of cases in which the evil of terrorism is outweighed by the good which could not be achieved in a less morally costly way, in practice, utilitarians often universally reject terrorism, because it is very dubious that acts of terrorism achieve significant good in a utility-efficient manner, or that the "harmful effects of undermining the convention of non-combatant immunity is thought to outweigh the goods that may be achieved by particular acts of terrorism". Among the non-utilitarian philosophers, Michael Walzer argued that terrorism is always morally wrong, but at the same time, those who engaged in terrorism can be morally justified in one specific case: when "a nation or community faces the extreme threat of complete destruction and the only way it can preserve itself is by intentionally targeting non-combatants, then it is morally entitled to do so".

In his book "Inside Terrorism" Bruce Hoffman wrote in Chapter One: Defining Terrorism that

"On one point, at least, everyone agrees: terrorism is a pejorative term. It is a word with intrinsically negative connotations that is generally applied to one's enemies and opponents, or to those with whom one disagrees and would otherwise prefer to ignore. 'What is called terrorism,' Brian Jenkins has written, `'thus seems to depend on one's point of view. Use of the term implies a moral judgment; and if one party can successfully attach the label terrorist to its opponent, then it has indirectly persuaded others to adopt its moral viewpoint.' Hence the decision to call someone or label some organization `terrorist' becomes almost unavoidably subjective, depending largely on whether one sympathizes with or opposes the person/group/cause concerned. If one identifies with the victim of the violence, for example, then the act is terrorism. If, however, one identifies with the perpetrator, the violent act is regarded in a more sympathetic, if not positive (or, at the worst, an ambivalent) light; and it is not terrorism."

The pejorative connotations of the word can be summed up in the aphorism, "One man's terrorist is another man's freedom fighter". This is exemplified when a group using irregular military methods is an ally of a state against a mutual enemy, but later falls out with the state and starts to use those methods against its former ally. During World War II, the Malayan People’s Anti-Japanese Army was allied with the British, but during the Malayan Emergency, members of its successor (the Malayan Races Liberation Army), were branded "terrorists" by the British. More recently, Ronald Reagan and others in the American administration frequently called the Afghan Mujahideen "freedom fighters" during their war against the Soviet Union, yet twenty years later, when a new generation of Afghan men are fighting against what they perceive to be a regime installed by foreign powers, their attacks are labelled "terrorism" by George W. Bush. Groups accused of terrorism understandably prefer terms reflecting legitimate military or ideological action.Leading terrorism researcher Professor Martin Rudner, director of the Canadian Centre of Intelligence and Security Studies at Ottawa's Carleton University, defines "terrorist acts" as attacks against civilians for political or other ideological goals, and goes on to say:

"There is the famous statement: 'One man's terrorist is another man's freedom fighter.' But that is grossly misleading. It assesses the validity of the cause when terrorism is an act. One can have a perfectly beautiful cause and yet if one commits terrorist acts, it is terrorism regardless."

Some groups, when involved in a "liberation" struggle, have been called "terrorists" by the Western governments or media. Later, these same persons, as leaders of the liberated nations, are called "statesmen" by similar organizations. Two examples of this phenomenon are the Nobel Peace Prize laureates Menachem Begin and Nelson Mandela.

Sometimes states which are close allies, for reasons of history, culture and politics, can disagree over whether or not members of a certain organization are terrorists. For instance, for many years, some branches of the United States government refused to label members of the Irish Republican Army (IRA) as terrorists while the IRA was using methods against one of the United States' closest allies (Britain) which Britain branded as terrorism. This was highlighted by the Quinn v. Robinson case.

For these and other reasons, media outlets wishing to preserve a reputation for impartiality are extremely careful in their use of the term.

Types

In the spring of 1975, the Law Enforcement Assistant Administration in the United States formed the National Advisory Committee on Criminal Justice Standards and Goals. One of the five volumes that the committee was entitled Disorders and Terrorism, produced by the Task Force on Disorders and Terrorism under the direction H.H.A. Cooper, Director of the Task Force staff. The Task Force classified terrorism into six categories.

* Civil Disorders – A form of collective violence interfering with the peace, security, and normal functioning of the community.

* Political Terrorism – Violent criminal behaviour designed primarily to generate fear in the community, or substantial segment of it, for political purposes. * Non-Political Terrorism – Terrorism that is not aimed at political purposes but which exhibits “conscious design to create and maintain high degree of fear for coercive purposes, but the end is individual or collective gain rather than the achievement of a political objective.”

* Quasi-Terrorism – The activities incidental to the commission of crimes of violence that are similar in form and method to genuine terrorism but which nevertheless lack its essential ingredient. It is not the main purpose of the quasi-terrorists to induce terror in the immediate victim as in the case of genuine terrorism, but the quasi-terrorist uses the modalities and techniques of the genuine terrorist and produces similar consequences and reaction. For example, the fleeing felon who takes hostages is a quasi-terrorist, whose methods are similar to those of the genuine terrorist but whose purposes are quite different.

* Limited Political Terrorism – Genuine political terrorism is characterized by a revolutionary approach; limited political terrorism refers to “acts of terrorism which are committed for ideological or political motives but which are not part of a concerted campaign to capture control of the State.

* Official or State Terrorism –"referring to nations whose rule is based upon fear and oppression that reach similar to terrorism or such proportions.” It may also be referred to as Structural Terrorism defined broadly as terrorist acts carried out by governments in pursuit of political objectives, often as part of their foreign policy.

In an analysis prepared for U.S. Intelligence four typologies are mentioned.

* Nationalist-Separatist

* Religious Fundamentalist

* New Religious

* Social Revolutionary

Democracy and domestic terrorism

The relationship between domestic terrorism and democracy is complex. Such terrorism is most common in nations with intermediate political freedom and that the nations with the least terrorism are the most democratic nations. However, one study suggests that suicide terrorism may be an exception to this general rule. Evidence regarding this particular method of terrorism reveals that every modern suicide campaign has targeted a democracy- a state with a considerable degree of political freedom. The study suggests that concessions awarded to terrorists during the 1980s and 1990s for suicide attacks increased their frequency.

Some examples of "terrorism" in non-democracies include ETA in Spain under Francisco Franco, the Shining Path in Peru under Alberto Fujimori, the Kurdistan Workers Party when Turkey was ruled by military leaders and the ANC in South Africa. Democracies, such as the United States, Israel, and the Philippines, also have experienced domestic terrorism.

While a democratic nation espousing civil liberties may claim a sense of higher moral ground than other regimes, an act of terrorism within such a state may cause a perceived dilemma: whether to maintain its civil liberties and thus risk being perceived as ineffective in dealing with the problem; or alternatively to restrict its civil liberties and thus risk delegitimizing its claim of supporting civil liberties. This dilemma, some social theorists would conclude, may very well play into the initial plans of the acting terrorist(s); namely, to delegitimize the state.

Islamic terrorism

Islamic terrorism is religious terrorism by groups or individuals, the motivation of which is typically rooted in the Qur'an or other Islamic tenets of faith. Terrorist acts have included airline hijacking, kidnapping, assassination and suicide bombing.

The hijacking of four passenger jets and the destruction of the World Trade Center on September 11 2001, in the United States of America was a significant attack. The controversies surrounding the subject include whether the terrorist act is self-defense or aggression, national self-determination or Islamic supremacy; whether Islam can ever condone the targeting of noncombatants; whether some attacks described as Islamic terrorism are merely terrorist acts committed by Muslims or motivated by nationalism; whether Zionism and the Arab-Israeli Conflict is the root of Islamic terrorism, or simply one cause; how much support there is in the Muslim world for Islamic terrorism and whether support for terror is a temporary phenomenon, a "bubble", now fading away.

Perpetrators

The perpetrators of acts of terrorism can be individuals, groups, or states. According to some definitions, clandestine or semi-clandestine state actors may also carry out terrorist acts outside the framework of a state of war. However, the most common image of terrorism is that it is carried out by small and secretive cells, highly motivated to serve a particular cause and many of the most deadly operations in recent times, such as the September 11 attacks, the London underground bombing, and the 2002 Bali bombing were planned and carried out by a close clique, composed of close friends, family members and other strong social networks. These groups benefited from the free flow of information and efficient telecommunications to succeed where others had failed.Over the years, many people have attempted to come up with a terrorist profile to attempt to explain these individuals' actions through their psychology and social circumstances. Others, like Roderick Hindery, have sought to discern profiles in the propaganda tactics used by terrorists. Some security organizations designate these groups as violent non-state actors.

It has been found that a "terrorist" will look, dress, and behave like a normal person, until he or she executes the assigned mission. Terrorist profiling based on personality, physical, or sociological traits would not appear to be particularly useful. The physical and behavioral description of the terrorist could describe almost any normal person.[58]

State sponsors

A state can sponsor terrorism by funding or harboring a terrorist organization. Opinions as to which acts of violence by states consist of state-sponsored terrorism or not vary widely. When states provide funding for groups considered by some to be terrorist, they rarely acknowledge them as such.

State terrorism

“Civilization is based on a clearly defined and widely accepted yet often unarticulated hierarchy. Violence done by those higher on the hierarchy to those lower is nearly always invisible, that is, unnoticed. When it is noticed, it is fully rationalized. Violence done by those lower on the hierarchy to those higher is unthinkable, and when it does occur is regarded with shock, horror, and the fetishization of the victims. ”

— Derrick Jensen [59]

The concept of state terrorism is controversial. The Chairman of the United Nations Counter-Terrorism Committee has stated that the Committee was conscious of the 12 international Conventions on the subject, and none of them referred to State terrorism, which was not an international legal concept. If States abused their power, they should be judged against international conventions dealing with war crimes, international human rights and international humanitarian law. Former United Nations Secretary-General Kofi Annan has said that it is "time to set aside debates on so-called 'state terrorism'. The use of force by states is already thoroughly regulated under international law"However, he also made clear that, "...regardless of the differences between governments on the question of definition of terrorism, what is clear and what we can all agree on is any deliberate attack on innocent civilians, regardless of one's cause, is unacceptable and fits into the definition of terrorism."

State terrorism has been used to refer to terrorist acts by governmental agents or forces. This involve the use of state resources employed by a state's foreign policies, such as the using its military to directly perform acts of considered to be state terrorism. Professor of Political Science, Michael Stohl cites the examples that include Germany’s bombing of London and the U.S. atomic destruction of Hiroshima during World War II. He argues that “the use of terror tactics is common in international relations and the state has been and remains a more likely employer of terrorism within the international system than insurgents." They also cite the First strike option as an example of the "terror of coercive diplomacy" as a form of this, which holds the world "hostage,' with the implied threat of using nuclear weapons in "crisis management." They argue that the institutionalized form of terrorism has occurred as a result of changes that took place following World War ll. In this analysis, state terrorism exhibited as a form of foreign policy was shaped by the presence and use of weapons of mass destruction, and that the legitimizing of such violent behavior led to an increasingly accepted form of this state behavior. (Michael Stohl, “The Superpowers and International Terror” Paper presented at the Annual Meeting of the International Studies Association, Atlanta, March 27-April 1, 1984;"Terrible beyond Endurance? The Foreign Policy of State Terrorism." 1988;The State as Terrorist: The Dynamics of Governmental Violence and Repression, 1984 P49).

State terrorism has also been used to describe peace time actions by governmental agents or forces, such as the bombing of Pan Am Flight 103 flight. Charles Stewart Parnell described William Gladstone's Irish Coercion Act as terrorism in his "no-Rent manifesto" in 1881, during the Irish Land War. The concept is also used to describe political repressions by governments against their own civilian population with the purpose to incite fear. For example, taking and executing civilian hostages or extrajudicial elimination campaigns are commonly considered "terror" or terrorism, for example during Red Terror or Great Terror. Such actions are often also described as democide which has been argued to be equivalent to state terrorism. Empirical studies on this have found that democracies have little democide.