The word terrorism may conjure images of a train ripped apart by an explosion as innocent families lie bleeding, the destruction of a suicide bomb in a busy mall, or frightened passengers in a plane hijacking.

Key points: Terrorist attacks committed by Muslims receive 357 per cent more media attention than those committed by non-Muslims

Terrorist attacks committed by Muslims receive 357 per cent more media attention than those committed by non-Muslims Less than one per cent of deaths from terrorism occur in developed countries

Less than one per cent of deaths from terrorism occur in developed countries In a ranking of countries most impacted by terrorism, Australia comes in at number 65

But how many of us picture a scene outside of the developed world?

On December 16, 2014, as Australians watched in horror the events of the Lindt Café siege in Sydney that claimed two innocent lives, an attack on a school in Pakistan left 145 dead — 132 of them children.

The same day in Yemen, 25 were killed in a double bombing that hit civilian targets that included a school bus. The day before the Sydney siege, 185 were kidnapped, including entire families, from a village in Nigeria.

Since the year 2000, more than 99 per cent of global deaths from terrorism occurred in impoverished countries already dealing with conflict or political terror, according to the US-based Global Terrorism Index (GTI).

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In the GTI's ranking of countries most impacted by terrorism, the US came in at number 32 and Australia 65.

So what is terrorism and, if it predominantly occurs elsewhere, how have so many of us come to associate the word with an Islamic attack on the West?

Why are so many 'terrorist' groups Islamic?

The Islamic State group has networks in at least 15 countries. ( REUTERS: Dado Ruvic )

Most nations and the UN have their own official lists of designated terrorist organisations.

The 26 terrorist organisations on Australia's watch list Al Qaeda — Four Al Qaeda branches and four affiliates of the group — including Somalia's Al Shabaab — have been designated terror groups by the Australian Government

Four Al Qaeda branches and four affiliates of the group — including Somalia's Al Shabaab — have been designated terror groups by the Australian Government Islamic State — Six branches of IS, also known as ISIS or ISIL, make the list. A further four have sworn allegiance to IS, including the notorious student-kidnapping central African group Boko Haram

Six branches of IS, also known as ISIS or ISIL, make the list. A further four have sworn allegiance to IS, including the notorious student-kidnapping central African group Boko Haram Kurdish Workers Party (PKK) — The only non-Islamic group to make the list are Turkey's PKK. The United States and allies, including Australia, have armed and trained branches of the PKK in Iraq and Syria despite continuing to officially condemn the Kurdish organisation as a terrorist group

The only non-Islamic group to make the list are Turkey's PKK. The United States and allies, including Australia, have armed and trained branches of the PKK in Iraq and Syria despite continuing to officially condemn the Kurdish organisation as a terrorist group Hezbollah — Out of the 25 Islamic organisations listed, Lebanon's Hezbollah — who hold close ties with Iran — are the only Shia group designated by Australia

Out of the 25 Islamic organisations listed, Lebanon's Hezbollah — who hold close ties with Iran — are the only Shia group designated by Australia Palestine's Hamas — Two Palestinian groups, Hamas and the Palestinian Islamic Jihad, have been designated for their attacks on Israeli citizens

In past eras, the focus has been on anarchists, Neo-Nazis, communists, left-wing organisations and even radical environmentalists.

In the US, right-wing extremists account for almost twice as many terrorist incidents as Muslims, according to a 2017 report by The Investigative Fund at The Nation Institute.

In the UK, it's often Northern Irish separatists, like the IRA.

But the majority of media coverage we see on terrorism today focuses on radical Islam.

Research by the University of Alabama showed terrorist attacks committed by non-Muslims receive an average of 15 press reports, while those committed by Muslim extremists receive 105; that is 357 per cent more media attention.

In Australia, 25 of the 26 designated terrorist organisations are Islamic.

Within Australian borders, we have no insurgent groups or armed opposition, but, in recent years, the majority of wars Australia has been involved in have been fought within Muslim countries.

Australian defence forces are currently deployed in at least five majority Muslim nations, including Afghanistan, Iraq and Syria.

What is terrorism and how is it defined?

More than 99 per cent of deaths from terrorism occur in developing countries. ( Al Hayat )

In Australia, adding a group to the terrorism list requires a long legislative process.

While the designation of some groups may seem straightforward — like Islamic State who openly embrace the use of terror with increasingly macabre executions and calls for global jihad — the labelling of others have political motivations not linked to national security.

"Defining a group as a terrorist organisation is an intrinsically political act," Charles Lister, the Middle East Institute's director of extremism and counterterrorism, told the ABC.

This has made finding a universally agreed on definition of terrorism a task that has eluded the UN for decades, he said.

The Oxford dictionary defines terrorism as "the unlawful use of violence and intimidation, especially against civilians, in the pursuit of political aims."

By this definition alone, things become murky.

Not only radical groups use terror tactics

Hundreds of thousands of civilians have been killed and injured in strikes deliberately targeting civilians by all sides of the Syrian conflict. ( Supplied )

Violence is by no means a tactic reserved for radicalised groups.

In Syria, several opposition groups have been designated internationally as terrorist organisations for attacks on civilian areas.

But airstrikes have claimed the lives of far more civilians as the Syrian Government and its allies continue the struggle to suppress an uprising.

"Yes, dropping a massive bomb on an urban populated area is just as terrifying universally as the prospect of being hit by a suicide bombing," Mr Lister said.

"They are both just as random. They are both just as destructive and they are both just as deadly."

Even Australian forces and their allies have been responsible for the deaths of civilians in strikes on Iraq and Syria.

As a member of a US-led coalition, Australia had "dropped thousands of munitions on targets in Iraq and Syria since August 2014", according to the Human Rights Watch.

Airstrikes by US-led coalition forces, including Australia, have claimed civilian lives in Syria. ( AP: Lefteris Pitarakis )

Significant terror attacks on Australian soil: September 1972 — Croatian separatists were believed responsible for bombing a Yugoslav agency in Sydney's Haymarket injuring 16

Croatian separatists were believed responsible for bombing a Yugoslav agency in Sydney's Haymarket injuring 16 February 1978 — A bomb targeting a government meeting at the Sydney Hilton Hotel left three dead and 11 injured

A bomb targeting a government meeting at the Sydney Hilton Hotel left three dead and 11 injured December 1980 — An attack claimed by the Justice Commandos of the Armenian Genocide took the lives of the Turkish Consul General and his secretary, while a bomb targeting the Melbourne Turkish Consulate in 1986 killed only the bomber

An attack claimed by the Justice Commandos of the Armenian Genocide took the lives of the Turkish Consul General and his secretary, while a bomb targeting the Melbourne Turkish Consulate in 1986 killed only the bomber 1980-1985 — A series of attacks on officials associated with the Family Court of Australia left four dead

A series of attacks on officials associated with the Family Court of Australia left four dead 1980's — Targeted bombings and attacks on the Asian population of WA were carried out for more than a decade by neo-Nazi group The Australian National Movement

Targeted bombings and attacks on the Asian population of WA were carried out for more than a decade by neo-Nazi group The Australian National Movement July 2001 — An anti-abortion attack on a clinic in Melbourne left one man dead

An anti-abortion attack on a clinic in Melbourne left one man dead December 2014 — The Lindt Cafe siege left three dead, including the perpetrator, and four injured

The Lindt Cafe siege left three dead, including the perpetrator, and four injured 2014-2018 — A series of Islamic motivated shootings and stabbings have claimed three innocent lives and injured 10

HRW report went on to name Australia as "the least transparent member of the coalition" in reporting civilian casualties.

So what differentiates an act of war from an act of terrorism, if not civilian casualties?

Mr Lister said what we have come to define as terrorism is often more about the tactics used and cultural perceptions than the result of the attack.

For many, a suicide bombing is a defining factor, regardless of whether or not the target is solely military.

"Committing suicide to kill others … it's something that just doesn't fit into our cultural psyche or something we can relate to," Mr Lister said.

But in the Middle East, an act of martyrdom in warfare "isn't quite such a taboo".

For some, when used against a military target, it is considered the ultimate sacrifice and a more respectable and discriminate means of warfare than indiscriminately dropping a barrel bomb on a city.

In lieu of a clear criteria to define a terrorist group, the label has become a way of listing not only threats to national security, but also as a way of forging political alliances.

The curious case of the PKK

Despite fighting under various names including YPG, YPJ, PYD and SDF, the biggest Kurdish faction in Syria follow PKK leader Abdullah Ocalan. ( ABC News: Tracey Shelton )

While Islamic State and Al Qaeda are predictably the two most internationally designated terror groups, the third may come as a surprise.

The Kurdish Workers Party, known widely by the acronym PKK, has been on the terrorist list of major countries across the globe for some decades.

Yet the US, Australia and European nations have been arming, training and supporting branches of this group in Syria and Iraq.

PKK are secular with a unique ideology that centres around somewhat Marxist views with a major focus on the empowerment of women.

Established by leader Abdullah Ocalan in 1978, the group took up arms in 1984 with the aim of creating an autonomous Kurdish state in Turkey by force.

But while PKK does pose an ongoing threat to Turkish national security, they have posed no threat to the majority of nations that have designated them as terrorists.

The decision was a political move to appease NATO partner Turkey, Mr Lister said, adding, "the crux of the whole problem is just how political the designation is".

Yet after arming them in the fight against another designated terrorist group, Islamic State, Australia, the US and others have not removed PKK from their terror lists.

Kurdish forces have been crucial in ground offensives against Islamic State in Syria and Iraq. ( ABC News: Tracey Shelton )

Mr Lister said it was not a question of their relevance in the fight against IS.

"Whether we like it or not — legally the PKK are a terrorist organisation so these countries should be basing their decisions according to their own laws," he said.

"We designated them for political reasons but we also chose to ignore the designation for political reasons."

"If we can choose to ignore it the entire act of designation seems to be in question."

Insurgents or terrorists?

US, Australian and allied governments have armed and trained branches of the PKK despite designating them as a terrorist group. ( AP: Syrian Democratic Forces )

"Increasingly, what we label terrorist groups or fighting terrorism is really just insurgencies within civil, local or regional conflicts," Mr Lister said.

While groups like Al Qaeda may speak of a global jihad, on a local level for those who join this movement "it's not about bombing New York it's about protecting their villages", he added.

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But attacks on such groups by foreign states can motivate terrorist ambitions abroad.

Designating them as terrorist organisations stifles negotiation and creates an us versus them mentality, said Joost Hiltermann, International Crisis Group MENA program director.

"It is short-sighted and self-defeating to not be open to the idea that these groups can evolve and can be made to evolve," Mr Hiltermann told the ABC.

"This is a better strategy than seeking to defeat them, which can be very difficult when they have popular local support."

Blocking negotiations through labels makes it difficult to pursue a peaceful solution.

We need to start looking at the root causes that make them locally relevant, Mr Lister said.

"Until we start to broaden our understanding of what these movements are, we are going to continue to play whack-a-mole, which is what we have been doing for years."

Editor's Note: This story has been edited to clarify the reasons for the listing of Hamas and Islamic Jihad as terrorist organisations and a sentence which could have been interpreted as suggesting Australian forces in Syria have breached international law has been deleted.