Sunni is the largest denomination of Islam. The set of beliefs is referred to as Sunnism or more properly Ahl al-Sunnah wa al-Jamā‘h (Arabic: أهل السنة والجماعة) (people of the example (of Muhammad) and the community), or Ahl al-Sunnah (Arabic: أهل السنة ) for short. The word Sunni comes from the word Sunnah (Arabic : سنة ), which means the words and actions  or example of the prophet Muhammad.
Historically, the Sunni faith has often been defined only in contrast with other denominations or schools of thought, such as Shia, Hanafiyah, Mu'tazila and others, considering itself to be the orthodox form of Islam. As such, a case is sometimes made that Sunnism is as old as Islam itself, or at least dates back to the first civil war in Islam from 656 to 661. However, in terms of doctrine and theology, and in the sense of considering itself a separate denomination, Sunnism is younger than that, making it somewhat misleading to talk about Sunnis in a 7th century context.
Sunnism was under the authority of the Caliph from Muhammad's death in 632 until the abolition of the caliphate by Mustafa Kemal Atatürk in 1924. Since then, no central international authority exists; many countries have a Grand Mufti or other official who holds the highest religious authority in the country. However, during all of Islam's history, independent religious scholars - the ulema - have held great influence in religious matters. During the first centuries of Islam, when the Umayyad and Abbasid caliphs were the worldly rulers of the Muslim world as well as the highest religious authorities of the Sunni faith, this led to some power struggles between the caliphate and the ulema. As the worldly power of the caliphate declined from the 9th and 10th century onwards, and as the religious law became more codified and exhaustive due to the efforts of the ulema, the caliphate's religious influence decreased as well.
There are many challenges to demographers attempting to calculate the proportion of the world's Muslim population who adhere to each of the main traditions. For instance, there is no Sunni–Shi'a breakdown available for many countries, and the CIA World Factbook gives a Sunni–Shi'a breakdown only for countries where Shi'a are a significant minority. When no breakdown is given, all the country's Muslims have been enrolled, provisionally, in the Sunni column. Thus, the exact percentage of the world's Muslim population that adheres to the various Shi'a sects, as opposed to the majority Sunni groups, is indeterminate. Therefore, using various sources, one can arrive at an estimate of anywhere from a low of 7.5%  to a high of 10% Shi'ite depending on the sources.
Sunni schools of law (Madhhab)
Islamic law is known as the Shari'ah. The Shari'ah is based on the Quran and the Sunnah, and those who ascribe to different interpretations of the law can often be found attending the same mosques (Masjids).
The four major Sunni schools of law and their respective founders are:
- Hanafi School (founded by Abu Hanifa)
Abu Hanifa (d. 767), was the founder of the Hanafi school. He was born circa 702 in Kufa, Iraq. Muslims of Bangladesh, Pakistan, India, Afghanistan, Central Asia, Muslim areas Southern Russia, The Caucasus, parts of The Balkans,Iraq and Turkey follow this school.
- Maliki School (founded by Malik ibn Anas)
Malik ibn Anas(d. 795) developed his ideas in Medina, where he knew some of the last surviving companions of the Prophet or their immediate descendents. His doctrine is recorded in the Muwatta which has been adopted by most Muslims of Africa except in Lower Egypt, Zanzibar and South Africa. The Maliki legal school is the branch of Sunni that dominates most of the Muslim areas of Africa, except Egypt and the Horn of Africa.
- Shafi'i School (founded by Muhammad ibn Idris ash-Shafi`i)
Al-Shafi'i (d. 820) was considered a moderate in most areas. He taught in Iraq and then in Egypt. Muslims in Indonesia, Lower Egypt, Malaysia, Somalia, Jordan, Lebanon, Syria, Palestine and Yemen follow this school. Al-Shafi'i placed great emphasis on the Sunnah of the Prophet, as embodied in the Hadith, as a source of the Shari'ah.
- Hanbali School (founded by Ahmad bin Hanbal)
Ahmad ibn Hanbal (d. 855) was born in Baghdad. He learned extensively from al-Shafi'i. Despite persecution, he held to the doctrine that the Qur'an was uncreated. This school of law is followed primarily in the Arabian Peninsula.
These four schools are somewhat different from each other, but Sunni Muslims generally consider them all equally valid. There are other Sunni schools of law. However, many are followed by only small numbers of people and are relatively unknown due to the popularity of the four major schools; also, many have died out or were not sufficiently recorded by their followers to survive.
Interpreting the Shari'ah to derive specific rulings (such as how to pray) is known as fiqh, which literally means understanding. A madhhab is a particular tradition of interpreting fiqh. These schools focus on specific evidence (Shafi'i and Hanbali) or general principles (Hanafi and Maliki) derived from specific evidences. The schools were started by eminent Muslim scholars in the first four centuries of Islam. As these schools represent clearly spelled out methodologies for interpreting the Shari'ah, there has been little change in the methodology per se. However, as the social and economic environment changes, new fiqh rulings are being made. For example, when tobacco appeared it was declared as 'disliked' because of its smell. When medical information showed that smoking was dangerous, that ruling was changed to 'forbidden'. Current fiqh issues include things like downloading pirated software and cloning. The consensus is that the Shari'ah does not change but fiqh rulings change all the time. A madhhab is not to be confused with a religious sect. There may be scholars representing all four madhhabs living in larger Muslim communities, and it is up to those who consult them to decide which school they prefer.
Many Sunnis advocate that a Muslim should choose a single madhhab and follow it in all matters. However, rulings from another madhhab are considered acceptable as dispensations (rukhsa) in exceptional circumstances. Some Sunnis, however, do not follow any madhhab. Indeed, some Salafis reject strict adherence to any particular school of thought, preferring to use the Qur'an and the Sunnah alone as the primary sources of Islamic law.
Sunni theological traditions
Some Islamic scholars faced questions that they felt were not specifically answered in the Qur'an, especially questions with regard to philosophical conundra like the nature of God, the existence of human free will, or the eternal existence of the Qur'an. Various schools of theology and philosophy developed to answer these questions, each claiming to be true to the Qur'an and the Muslim tradition (sunnah). Among Sunnites, the following were the dominant traditions:
- Ash'ari, founded by Abu al-Hasan al-Ash'ari (873–935). This theology was embraced by Muslim scholars such as al-Ghazali.
- Ash'ariyyah theology stresses divine revelation over human reason. Ethics, they say, cannot be derived from human reason: God's commands, as revealed in the Qur'an and the practice of Muhammad and his companions (the sunnah, as recorded in the traditions, or hadith), are the source of all morality.
- Regarding the nature of God and the divine attributes, the Ash'ari rejected the Mu'tazilite position that all Qur'anic references to God as having physical attributes (that is, a body) were metaphorical. Ash'aris insisted that these attributes were "true", since the Qur'an could not be in error, but that they were not to be understood as implying a crude anthropomorphism.
- Ash'aris tend to stress divine omnipotence over human free will. They believe that the Qur'an is eternal and uncreated.
- Maturidiyyah, founded by Abu Mansur al-Maturidi (d. 944). Maturidiyyah was a minority tradition until it was accepted by the Turkish tribes of Central Asia (previously they had been Ashari and followers of the Shafi school, it was only later on migration into Anatolia that they became Hanafi and followers of the Maturidi creed). One of the tribes, the Seljuk Turks, migrated to Turkey, where later the Ottoman Empire was established. Their preferred school of law achieved a new prominence throughout their whole empire although it continued to be followed almost exclusively by followers of the Hanafi school while followers of the Shafi, Maliki, and Hanbali schools within the empire followed the Ashari school. Thus, wherever can be found Hanafi followers, there can be found the Maturidi creed.
- Maturidiyyah argue that knowledge of God's existence can be derived through reason.
- Athariyyah (meaning Textualist) or Hanbali. No specific founder, but Imam Ahmad ibn Hanbal played a key historic role in keeping this school alive.
- This school differs with the Ash'ariyyah in understanding the names and attributes of God, but rather affirms all of God's names and attributes as they are found in the Qur'an and Sunnah (prophetic traditions), with the disclaimer that the "how" of the attribute is not known. They say that God is as He described Himself "in a way befitting of His majesty." Thus, regarding verses where God is described as having a yad (hand) or wajh (face), the textualists say that God is exactly as He described himself in a way befitting of His majesty, without inquiring as to the "how" of these attributes.
- The Athariyyah still believe that God does not resemble His creation in any way, as this is also found in the texts. Thus, in the Athari creed, it is still prohibited to imagine an image of God in any way. The Athariyyah say that the yad" (hand) of God is "unlike any other yad" (since God does not resemble His creation in any way) and prohibit imagining what God would be like, even though this attribute of a yad is still affirmed.
- This is the view of Imam Ahmad ibn Hanbal who said: "The hadiths (regarding the attributes of Allah) should be left as they are... We affirm them, and we do not make any similitude for them. This is what has been agreed upon by the scholars."
Sunni view of hadith
The Qur'an as we have it today was compiled by Muhammad's companions (Sahaba) in approximately 650, and is accepted by all Muslim denominations. However, there were many matters of belief and daily life that were not directly prescribed in the Qur'an, but were actions that were observed by the prophet and the community. Later generations sought out oral traditions regarding the early history of Islam, and the practice of Muhammad and his first followers, and wrote them down so that they might be preserved. These recorded oral traditions are called hadith. Muslim scholars sifted through the hadith and evaluated the chain of narration of each tradition, scrutinizing the trustworthiness of the narrators and judging the strength of each hadith accordingly. Most Sunni accept the hadith collections of Bukhari and Muslim as the most authentic (sahih, or correct), and grant a lesser status to the collections of other recorders. There are, however, four other collections of hadith that are also held in particular reverence by Sunni Muslims, making a total of six(6):
There are also other collections of hadith which, although less well-known, are still thought to contain many authentic hadith and are frequently used by specialists. Examples of these collections include:
- Muwatta of Imam Malik
- Musnad of Ahmad ibn Hanbal
- Sahih Ibn Khuzaima
- Sahih Ibn Hibban
- Mustadrak of Al Haakim
- Musannaf of Abd al-Razzaq
- Sunna - Definitions from Dictionary.com
- ""How Many Shia Are in the World?"". IslamicWeb.com. Retrieved on 2006-10-18.
- Josef W. Meri, Medieval Islamic Civilization: An Encyclopedia, 1 edition, (Routledge: 2005), p.5
- Hisham M. Ramadan, Understanding Islamic Law: From Classical to Contemporary, (AltaMira Press: 2006), p.26
- Bülent Þenay. "Ash'ariyyah Theology, Ashariyyah". 'BELIEVE Religious Information Source'. Retrieved on 2006-04-01.
- "Maturidiyyah". 'Philtar'. Retrieved on 2006-04-01.
- Reported by ibn al-Jawzi in Manaaqib Imam Ahmad, pg. 155-156.
- The belief of Ahl as-Sunnat
- Islamic Law Infobase
- University of Southern California, Compendium of Muslim Texts
- Fiqh al-Akbar by Imam Abu Hanifah
- Muwatta by Imam Malik
- Searchable Ar-Risala by Imam Shafi'i
- Foundations of the Sunnah, by Imam Ahmad ibn Hanbal
- Source Methodology in Islamic Jurisprudence (Usul al-Fiqh), by Taha Jabir Al 'Alwani