
Muslims are people who adhere to Islam, a monotheistic religion belonging to the Abrahamic tradition. They consider the Quran, the foundational religious text of Islam, to be the verbatim word of the God of Abraham as it was revealed to Muhammad, the main Islamic prophet. The majority of Muslims also follow the teachings and practices of Muhammad (sunnah) as recorded in traditional accounts (hadith).

Comparative religion is the branch of the study of religions with the systematic comparison of the doctrines and practices, themes and impacts of the world's religions. In general the comparative study of religion yields a deeper understanding of the fundamental philosophical concerns of religion such as ethics, metaphysics and the nature and forms of salvation. It also considers and compares the origins and similarities shared between the various religions of the world. Studying such material facilitates a broadened and more sophisticated understanding of human beliefs and practices regarding the sacred, numinous, spiritual and divine.

Christianity is the most widely professed religion in the United States, with Protestantism being its largest branch, although the country has rapidly secularized in recent years. According to the World Values Survey in 2017, the United States is more secular than the median country; they ranked the United States the 32nd least religious country in the world. A large variety of faiths have historically flourished within the country. Until the 1990s, the United States was a substantial outlier among other highly developed countries: uniquely combining a high level of religiosity and wealth, although this has lessened significantly since. Studies during the early 2020s found that about 81% of Americans believe in a higher power, 45% report praying on a daily basis, and 41% report that religion plays a very important role in their lives. A majority of Americans report "seldom" or "never" attending religious services; 31% report attending religious services weekly or near weekly. Trust in "the church or organized religion" has declined significantly since the 1970s. According to the Pew Research Center, 30% of Americans describe themselves as not being affilated with a religion; and lie in spectrum that ranges from materialistic forms of hard Atheism to forms of spirituality that deviate from traditional religious structures.
Religion in Africa is multifaceted and has been a major influence on art, culture and philosophy. Today, the continent's various populations and individuals are mostly adherents of Christianity, Islam, and to a lesser extent several traditional African religions. In Christian or Islamic communities, religious beliefs are also sometimes characterized with syncretism with the beliefs and practices of traditional religions.

World religions is a category used in the study of religion to demarcate the five—and in some cases more—largest and most internationally widespread religious movements. Hinduism, Buddhism, Judaism, Christianity, and Islam are always included in the list, being known as the "Big Five". Some scholars also include other world religions, such as Taoism, Jainism, Sikhism, Zoroastrianism, and the Baháʼí Faith, in the category. These are often juxtaposed against other categories, such as indigenous religions and new religious movements, which are also used by scholars in this field of research.

Religion in Norway is dominated by Lutheran Christianity, with 68.7% of the population belonging to the Evangelical Lutheran Church of Norway in 2019. The Catholic Church is the next largest Christian church at 3.1%. The unaffiliated make up 18.3% of the population. Islam is followed by 3.4% of the population.

Religion in Egypt controls many aspects of social life and is endorsed by law. The state religion of Egypt is Islam. Although estimates vary greatly in the absence of official statistics. Since the 2006 census religion has been excluded, and thus available statistics are estimates made by religious and non-governmental agencies. The country is majority Sunni Muslim, with the next largest religious group being Coptic Orthodox Christians. The exact numbers are subject to controversy, with Christians alleging that they have been systemically under-counted in existing censuses.

As of the year 2020, Christianity had approximately 2.4 billion adherents and is the largest-religion by population respectively. According to a PEW estimation in 2020, Christians made up to 2.4 billion of the worldwide population of about 7.7 billion people. It represents nearly one-third of the world's population and is the largest religion in the world, with the three largest groups of Christians being the Catholic Church, Protestantism, and the Eastern Orthodox Church. The largest Christian denomination is the Catholic Church, with 1.3 billion baptized members. The second largest Christian branch is either Protestantism, or the Eastern Orthodox Church.

Religion in Europe has been a major influence on today's society, art, culture, philosophy and law. The largest religion in Europe is Christianity, but irreligion and practical secularisation are strong. Three countries in Southeastern Europe have Muslim majorities. Ancient European religions included veneration for deities such as Zeus. Modern revival movements of these religions include Heathenism, Rodnovery, Romuva, Druidry, Wicca, and others. Smaller religions include the Dharmic religions, Judaism, and some East Asian religions, which are found in their largest groups in Britain, France, and Kalmykia.
Asia is the largest and most populous continent and the birthplace of many religions including Buddhism, Christianity, Confucianism, Hinduism, Islam, Jainism, Judaism, Shinto, Sikhism, Taoism, and Zoroastrianism. All major religious traditions are practiced in the region and new forms are constantly emerging. Asia is known for its diversity of culture. Islam and Hinduism are the largest religions in Asia with approximately 1.2 billion adherents each.
As of 2011, most Armenians in Armenia are Christians (97%) and are members of the Armenian Apostolic Church, which is one of the oldest Christian churches. It was founded in the 1st century AD, and in 301 AD became the first branch of Christianity to become a state religion.

Religion in Ethiopia consists of a number of faiths. Among these mainly Abrahamic religions, the most numerous is Christianity totaling at 67.3%, followed by Islam at 31.3%. There is also a longstanding but small Jewish community. Some adherents of the Baháʼí Faith likewise exist in a number of urban and rural areas. Additionally, there is also a substantial population of the adherents of traditional faiths.
Growth of religion involves the spread of individual religions and the increase in the numbers of religious adherents around the world. In sociology, desecularization is the proliferation or growth of religion, most commonly after a period of previous secularization. Statistics commonly measure the absolute number of adherents, the percentage of the absolute growth per-year, and the growth of converts in the world.

Christianity is the predominant religion in Uganda. According to the 2014 census, over 84 percent of the population was Christian, while about 14 percent of the population adhered to Islam, making it the largest minority religion. Anglicanism and Catholicism are the main Christian denominations in the country.
The Abrahamic religions are a group of religions centered around worship of the God of Abraham. Abraham, a Hebrew patriarch, is extensively mentioned throughout Abrahamic religious scriptures the Bible, Quran and Torah.
Islam is the most widely professed religion in Chad, with a significant minority adhering to Christianity. Smaller populations of non-religious people as well as adherents of other faiths are also present.
Islam is the most followed religion in Niger and is practiced by 99% of the population. According to Pew, roughly 80% of Muslims are Sunni of Maliki school of jurisprudence, whilst 20% are non-denominational Muslims, Other religions practiced in Niger include Animism and Christianity.

Christianity is the majority religion in Cameroon, with significant minorities of the adherents of Islam and traditional faiths.
Ethical monotheism is a form of exclusive monotheism in which God is believed to be the only god as well as the source for one's standards of morality, guiding humanity through ethical principles.
Religious syncretism is the blending of religious belief systems into a new system, or the incorporation of other beliefs into a religious tradition.