A religion is a set of practices, often centered upon specific supernatural and moral claims about reality, the cosmos, and human nature, and often codified as prayer, ritual, or religious law. Religion also encompasses ancestral or cultural traditions, writings, history, and mythology, as well as personal faith and religious experience. The term "religion" refers to both the personal practices related to communal faith and to group rituals and communication stemming from shared conviction.

In the frame of western religious thought, religions present a common quality, the "hallmark of patriarchal religious thought": the division of the world in two comprehensive domains, one sacred, the other profane. Religion is often described as a communal system for the coherence of belief focusing on a system of thought, unseen being, person, or object, that is considered to be supernatural, sacred, divine, or of the highest truth. Moral codes, practices, values, institutions, tradition, rituals, and scriptures are often traditionally associated with the core belief, and these may have some overlap with concepts in secular philosophy. Religion is also often described as a "way of life" or a life stance.

The development of religion has taken many forms in various cultures. "Organized religion" generally refers to an organization of people supporting the exercise of some religion with a prescribed set of beliefs, often taking the form of a legal entity. Other religions believe in personal revelation. "Religion" is sometimes used interchangeably with "faith" or "belief system,"but is more socially defined than that of personal convictions.

Religion has been defined in a wide variety of ways. Most definitions attempt to find a balance somewhere between overly sharp definition and meaningless generalities. Some sources have tried to use formalistic, doctrinal definitions while others have emphasized experiential, emotive, intuitive, valuational and ethical factors. Definitions mostly include:

a notion of the transcendent or numinous, often, but not always, in the form of theism
a cultural or behavioural aspect of ritual, liturgy and organized worship, often involving a priesthood, and societal norms of morality (ethos) and virtue (arete)
a set of myths or sacred truths held in reverence or believed by adherents
Sociologists and anthropologists tend to see religion as an abstract set of ideas, values, or experiences developed as part of a cultural matrix. For example, in Lindbeck's Nature of Doctrine, religion does not refer to belief in "God" or a transcendent Absolute. Instead, Lindbeck defines religion as, "a kind of cultural and/or linguistic framework or medium that shapes the entirety of life and thought… it is similar to an idiom that makes possible the description of realities, the formulation of beliefs, and the experiencing of inner attitudes, feelings, and sentiments.” According to this definition, religion refers to one's primary worldview and how this dictates one's thoughts and actions.

Other religious scholars have put forward a definition of religion that avoids the reductionism of the various sociological and psychological disciplines that reduce religion to its component factors. Religion may be defined as the presence of a belief in the sacred or the holy. For example Rudolf Otto's "The Idea of the Holy," formulated in 1917, defines the essence of religious awareness as awe, a unique blend of fear and fascination before the divine. Friedrich Schleiermacher in the late 18th century defined religion as a "feeling of absolute dependence."

In summary, it may be said that almost every known culture involves the religious in the above sense of a depth dimension in cultural experiences at all levels — a push, whether ill-defined or conscious, toward some sort of ultimacy and transcendence that will provide norms and power for the rest of life. When more or less distinct patterns of behaviour are built around this depth dimension in a culture, this structure constitutes religion in its historically recognizable form. Religion is the organization of life around the depth dimensions of experience — varied in form, completeness, and clarity in accordance with the environing culture."

 "A general term used... to designate all concepts concerning the belief in god(s) and goddess(es) as well as other spiritual beings or transcendental ultimate concerns" and "human beings' relation to that which they regard as holy, sacred, spiritual, or divine.

The main Religions of the World, mapped without denominations.. In summary, religious adherence of the world's population is as follows: "Abrahamic": 53.5%, "Indian": 19.7%, irreligious: 14.3%, "Far Eastern": 6.5%, tribal religions: 4.0%, new religious movements: 2.0%. Abrahamic religions are by far the largest group, and these consist primarily of Christianity, Islam and Judaism (sometimes the Bahá'í Faith is also included). They are named for the patriarch Abraham, and are unified by their strict monotheism. Today, around 3.4 billion people are followers of Abrahamic religions and are spread widely around the world apart from the regions around South-East Asia. Several Abrahamic organizations are vigorous proselytizers.
Indian religions originated in Greater India and tend to share a number of key concepts, such as dharma and karma. They are of the most influence across the Indian subcontinent, East Asia, South East Asia, as well as isolated parts of Russia. The main Indian religions are Hinduism, Buddhism, Sikhism, and Jainism. Indian religions mutually influenced each other. Sikhism was also influenced by the Abrahamic tradition of Sufism.
Far Eastern religions consist of several East Asian religions which make use of the concept of Tao (in Chinese) or Do (in Japanese or Korean). They include Taoism, Shinto, Chondogyo, Caodaism, and Yiguandao. Far Eastern Buddhism (in which the group overlaps with the "Indian" group) and Confucianism (which by some categorizations is not a religion) are also included.
Iranic religions originated in Iran and include Zoroastrianism, Yazdanism and historical traditions of Gnosticism (Mandaeanism, Manichaeism). It has significant overlaps with Abrahamic traditions, e.g. in Sufism and in recent movements such as Bábísm and the Bahá'í Faith.

African diasporic religions practiced in the Americas, imported as a result of the Atlantic slave trade of the 16th to 18th centuries, building of traditional religions of Central and West Africa.
Indigenous tribal religions, formerly found on every continent, now marginalized by the major organized faiths, but persisting as undercurrents of folk religion. Includes African traditional religions, Asian Shamanism, Native American religions, Austronesian and Australian Aboriginal traditions and arguably Chinese folk religion (overlaps with Far Eastern religions). Under more traditional listings, this has been referred to as "Paganism" along with historical polytheism.
New religious movements, a heterogeneous group of religious faiths emerging since the 19th century, often syncretizing, re-interpreting or reviving aspects of older traditions (Bahá'í, Hindu revivalism, Ayyavazhi, Pentecostalism, polytheistic reconstructionism), some inspired by science-fiction (UFO religions). See List of new religious movements, list of groups referred to as cults.
Demographic distribution of the major super-groupings mentioned is shown in the table below:

Name of Group Name of Religion Number of followers Date of Origin Main regions covered Abrahamic religions 3.6 billion

Christianity 2.1 billion 1st c. Worldwide except Northwest Africa, the Arabian Peninsula, and parts of Central, East, and Southeast Asia.

Islam 1.5 billion 7th c. Middle East, Northern Africa, Central Asia, South Asia, Western Africa, Indian subcontinent, Malay Archipelago with large population centers existing in Eastern Africa, Balkan Peninsula, Russia, Europe and China.

Judaism 14 million 1300 BCE >Israel and among Jewish diaspora (live mostly in USA, Canada, and Europe)

Bahá'í Faith 5 million 19th c. Dispersed worldwide with no major population centers

Indian religions 1.4 billion

Hinduism 900 million no founder Indian subcontinent, Fiji, Guyana and Mauritius
Buddhism 376 million Iron Age (1200–300 BCE) Indian subcontinent, East Asia, Indochina, regions of Russia.
Sikhism 25.8 million 15th c. India, Pakistan, Africa, Canada, USA, United Kingdom Jainism 4.2 million Iron Age (1200–300 BCE) India, and East Africa

Far Eastern religions
500 million Taoism unknown Spring and Autumn Period (722 BC-481 BC) China and the Chinese diaspora
Confucianism unknown Spring and Autumn Period (722 BC-481 BC) China, Korea, Vietnam and the Chinese and Vietnamese diasporas
Shinto 4 million no founder Japan
Caodaism 1-2 million 1925 Vietnam
Chondogyo 1.13 million 1812 Korea
Yiguandao 1-2 million c. 1900 Taiwan
Chinese folk religion 394 million no founder, a combination of Taoism, Confucianism and Buddhism China
Ethnic/tribal 400 million
Primal indigenous 300 million no founder India, Asia
African traditional and diasporic 100 million no known founder Africa, Americas
Other
each over 500 thousand
Juche 19 million  North Korea
Spiritism 15 million  
Neopaganism 1 million  
Unitarian-Universalism 800,000  
Rastafarianism 600,000  
Scientology 500,000