Islam is a monotheistic Abrahamic religion based on the Quran, which adherents believe to be the literal word of God (Allah) as revealed to the Prophet Muhammad in the 7th century CE, and on the hadith, records of Muhammad's sayings and actions. Islam is practiced by an estimated 1.9 billion people worldwide, making it the second-largest religion by adherents.1) Core beliefs and practices are organized (in Sunni formulations) around the Five Pillars: the declaration of faith (shahada), prayer (salat), almsgiving (zakat), fasting during Ramadan (sawm), and pilgrimage to Mecca (hajj); Shia Islam frames obligatory practice somewhat differently. The religion's historical and theological relationship to Christianity and Judaism is a recurring subject of both academic study and confessional debate; see islam-abrahamic-relationship-debate.
The two largest branches, Sunni and Shia Islam, diverge primarily over the question of rightful succession to Muhammad's leadership of the early Muslim community, a split with continuing theological and political significance. Smaller traditions include Sufism (often described as a mystical dimension of Islam rather than a separate branch), Ibadism, and various reformist and revivalist movements. Islamic legal and theological scholarship has produced multiple schools of jurisprudence (madhahib) that differ on matters of law and practice.
Islam today encompasses a wide range of doctrinal, legal, and cultural expressions across more than 50 majority-Muslim countries and substantial minority populations elsewhere.2) Contemporary discourse within and about Islam addresses questions including the interpretation of scripture in modern contexts, the relationship between religious law (sharia) and civil governance, the role of women, approaches to religious pluralism, and the diversity of practice across regions and communities. Academic, theological, and political disagreement persists over how representative any single interpretation is of the religion as a whole; see islam-representative-interpretation-debate.
The relationship between Islam and other Abrahamic traditions, including the role of rabbinic texts such as the Talmud in comparative religious scholarship, is itself a subject of differing scholarly and confessional viewpoints, ranging from emphasis on shared theological lineage to emphasis on doctrinal distinction; see islam-christianity-comparative-viewpoint and islam-judaism-comparative-viewpoint.
For historical background on Islam's origins, expansion, and major developments, see islam-history.