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Sen. Ted Cruz, when at last month's CNN town hall meeting to defend his controversial proposal to target Muslim neighborhoods in the United States, made a valuable distinction between Islam and Islamism.

Islam, the White House hopeful noted, is a religion, while Islamism is a political ideology. Cruz's elaboration, beyond this initial distinction, may garner less support from researchers examining Islamism in its multiple expressions, but the Texas senator can indeed be excused: These experts themselves are rarely in agreement about how to label and categorize their subject matter. When compared to the "Islam hates us" aside of another presidential , Cruz's remarks reflect an apparent attempt to understand a complex situation, rather than an effort to appeal to the primal fears of the electorate.

When it comes to Islam and Islamism, a multitude of terms and categorization schemes are in competition. Some are built upon known words and expressions, and may thus be easier to conceive -- such as Islamo-fascism and Islamic supremacism -- but they carry with them the effect of eliminating nuances by assuming undue similarities. Others, while hopefully more accurate, are too arcane for the non-specialists; often, even to the specialists, they may be too opaque without the assistance of copious footnotes.

Yet, for the sake of an informed political conversation, we may need to agree on the broader definition and usage of four terms: Islam, Islamism, radicalism, and jihadism. Used separately or in combination, these terms provide a sound definition of virtually all the expressions of the subject matter.

Islam is the religious tradition that shapes the faith and, to different degrees, the culture of its Muslim followers. Most Muslims believe in the unity of the Islamic truth, the message that Islam has delivered through the Prophet Muhammad. They do, however, disagree on the substance of this truth. Many doctrinal versions of Islam thus coexist. The most commonly mentioned division within Islam is the split between the Sunni and Shiite sects. But today's Sunni Muslims, at about -- possibly the largest denomination of any religion in history -- are not a homogeneous group, neither in their formal faith nor in their practice. The most religious among them range from the followers of ecstatic masters to disciples of literalist scholasticism, while the less religious are indistinguishable from their fellow citizens. At more than 200 million worldwide, Shiite Muslims display the same spectrum of religiosity as their Sunni counterparts, together with a parallel pattern in doctrinal variations.

In fact, it may be convenient to de-emphasize the Sunni-Shiite distinction in many contexts, and to introduce instead another scale, applicable to all. Muslims worldwide can be observed as being orthodox, conservative, or secular.

For orthodox Muslims, their identity is largely determined by their faith and religious practices. They are Muslims first, with other aspects of their life qualifying, but not overriding, their Muslim identity. In the United States, they would be American Muslims, and they can be fully committed patriots, or choose to separate themselves from others. In all cases, it is their understanding of their faith that frames their social and cultural mindset.

The overwhelming majority of the global Muslim population is better labeled as conservative. Their faith is of principal importance to them, but so is their country, culture, and community. And like most people, these priorities are imbued with elements of their faith. Irish Americans, for example, are more Irish on St Patrick's Day, and the Christian faithful more spiritual on Easter. All are, however, proud Americans on the Fourth of July. And so are conservative Muslims. They are Muslim Americans in the United States, Muslim Turks in Turkey, Muslim Indonesians in Indonesia, and Muslim French in France. They usually see no conflict between their faith and their culture, but if one were to emerge, loyalties would have to be deliberated. The Muslim French, for example, are not of one opinion on the banning of the Muslim scarf in public schools.

Secular Muslims may be a small minority, but they are influential. For this segment of the Muslim population, faith -- or the lack thereof -- is relegated to the private sphere. Their Islamic legacy is still appreciated, to different extents, but it is not essential in shaping their worldview. These are citizens from Muslim families or from an Islamic background who would generally accept the designation of Muslim with a qualifier: cultural Muslims, or non-practicing Muslims. Many, however, would prefer to avoid the application of the Muslim label altogether.

Whether Sunni or Shiite, orthodox, conservative, or secular, Muslims may or may not embrace any of the multitude of ideologies -- socialism, liberalism, nationalism, racism, anarchism, libertarianism, and so forth. And some orthodox and conservative Muslims may choose Islamism.

Islamism is a wide range of political ideologies that asserts that Islam, as a faith, ought to inform or shape the political order. In its softer forms, Islamism would seek to frame the political process with Islamic values such as piety, modesty, and social solidarity. At its most extreme, it may negate any institution or idea not rooted in Islamic dogma.

The conciliatory practice of Tunisia's Islamist party, Ennahda, after it won elections in 2011 is at one end of the Islamism spectrum. At the other end lies the Islamic State group, or ISIS, which engages in the material obliteration and physical elimination of anyone or anything not in compliance with its own understanding of the religious order.

Cruz was thus partially correct in expounding on Islamism. The Islamic State, but not Ennahda, would seek to subjugate or destroy the United States. He would have been more accurate had he qualified his use of the word Islamism. What sets Ennahda and other civic expressions of Islamism apart from the Islamic State, al-Qaida, and the political system of the Islamic Republic of Iran is that this latter group espouses radicalism.

Radicalism is the conviction that no compromise can be reached at the fundamental level between the non-Islamic order as it stands, and the desired religious vision. The Islamic State group and its companions can be viewed as expressions of radical Islamism. Beyond Islamism, some doctrinal variations in Islam as a religion, such as Salafism or Wahhabism, also preach the incompatibility between Islam and non-Islamic institutions, without suggesting a break with the existing political order. It may be appropriate to refer to them as radical Islam. It is often noted that radical Islam is a path toward radical Islamism. Some counter with the suggestion that radical Islam may actually be a path away from radical Islamism. For example, the deradicalization program in Saudi Arabia does not question the radical faith elements of the jihadists it attempts to reform. It merely underlines the religious commandment of accepting the judgment of the Saudi rulers in not seeking their application.

Radical Islamism is often expressed as jihadism. Jihad, in the Islamic tradition, has had multiple uses. In the 20th century, prior to the rise of Islamism, an emphasis was put on the non-violent meanings of jihad. It is fair to assume that this battle has been lost, at least for the time being. Today, jihad is warfare launched by Islamist non-state actors. Jihadism is the corollary of radical Islamism that considers that the defeat of the political order incompatible with Islam can only be achieved by force. Jihadist practice has varied, but it has rarely been in compliance with the conventional Islamic view of jihad as ‘just war.'

In sum, Islam is the religion in its diversity; Islamism is a range of political ideologies that demand Islam in the political practice; radical Islam is a form of the religion that objects to non-Islamic culture and institutions; radical Islamism adds the rejection of the non-Islamic political order; and jihadism is the use of force by non-state actors toward the achievement of Islamist goals.

2016 presidential candidates, take note: While Islamists and their ilk will no doubt continue to be of great concern to American voters, it is the responsibility of the country's leaders and elected officials to get the terminology right, and to do so without slandering an entire religion and its followers.