Ayatollah
Title given to a senior-ranking Shiite religious scholar.

Caliphate
The line of the Prophet Muhammad’s successors as the temporal and spiritual leaders of Islam after his death in the 7th century. The caliphate existed in one form or another from 632 until 1924, when the Ottoman caliphate officially ended.

Cemaat
Turkish variation of Arabic word ja’mat, which means community.

Da’wa
Preaching or, literally, “calling” (or “inviting”) Muslims and non-Muslims to embrace Islamic beliefs and practices.

Deobandism
A conservative school of Sunni theology founded in the second half of the 19th century and named for a seminary outside of Delhi, India. Deobandism is influential among many European Muslims of South Asian heritage, particularly through the Tablighi Jama’at movement.

Fatwa
A ruling or legal opinion on Islamic law issued by an Islamic scholar.

Fiqh
Islamic jurisprudence based on study of the Quran and other sacred texts.

Halal
Something that is lawful and permitted in Islam. Often used to refer to Islamic dietary laws, which prescribe ritual slaughtering of beef and poultry, among other things.

Imam
Used by many Muslims today as a title for the prayer leader at a mosque and/or the spiritual leader of a Muslim community. But Shiites also use the term in a very different way, to refer to descendants of the Prophet Muhammad whom they consider his rightful successors.

Islamist
An advocate of Islamism, a political ideology that calls for the establishment of a distinctly Islamic system of government through the direct implementation of Islamic religious law (shari’a).

Jihad
An Arabic word that translates as “struggle” or “striving.” It is traditionally used by Muslims to describe an inward, spiritual struggle for holiness and good, though it is also commonly used to describe military action in the name of Islam.

Madrasa
A Muslim place of learning usually associated with a mosque.

Marja
Among Shiites, a religious figure seen as a living example of Islam to be followed and admired. Shortened form of the Arabic marja’ al-taqlid, meaning “source of emulation.”

Murid
A Sufi devotee.

Murshid
A Sufi spiritual guide.

Salafism
A puritanical movement in Islam that emphasizes a conservative and literalist interpretation of scriptural sources. Literally followers of the salaf as-salih, or “pious predecessors,” Salafis emphasize exclusive reliance on the teachings of the early Muslims closest to the Prophet Muhammad. Classical Salafism is concerned almost exclusively with issues of creedal purity and the authenticity of scriptural sources, but in recent years Salafism has become cross-fertilized with overtly political groups.

Shari’a
The revealed and canonical laws of Islam.

Shaykh, sheikh or pir
The head of a Sufi order, generally a hereditary position, representing a spiritual genealogy tracking back to the Prophet Muhammad.

Shiism
One of the two main branches of Islam. The name is a shortened form of the historical term Shia-t-Ali, or “supporters of Ali,” and refers to one of the factions that emerged from a dispute over leadership succession soon after the death of the Prophet Muhammad in 632. Over time, the political divide between Shiites and Sunni Muslims broadened to include theological distinctions and differences in religious practice.

Sunni
The other main branch of Islam. Sunni Muslims make up at least 85% of the world’s Muslim population. The name comes from Ahl al-Sunna, or “people of the tradition,” and refers to established norms for Muslim conduct based on the sayings and actions of the Prophet Muhammad.

Tariqat
Literally meaning “paths,” mystical orders or brotherhoods of Sufis.

Umma
The world community of Muslim believers.

Wahhabi
A variant of the broader Salafi movement in Islam that has grown globally in recent years. Wahhabism is the official doctrine of Saudi Arabia’s religious establishment. It has its origins in the thinking of Muhammad Ibn Abdul Wahhab, an 18th century puritanical revivalist from central Arabia who formed an alliance with a forebear of the present Saudi ruling family.

Zhikr
Ritual chanting of God’s attributes.

Photo credit: Gérard Degeorge/CORBIS