Christianity is a monotheistic religion centered on the life and teachings of Jesus of Nazareth as presented in the New Testament. Christians believe Jesus to be the Son of God and the Messiah prophesied in the Old Testament. With an estimated 2.1 billion adherents in 2001, Christianity is the world's largest religion. It is the predominant religion in Europe, the Americas, Southern Africa, the Philippine Islands and Oceania. It is also growing rapidly in Asia, particularly in China and South Korea. Christianity shares its origins and many religious texts with Judaism, specifically the Hebrew Bible, known to Christians as the Old Testament.Like Judaism and Islam, Christianity is classified as an Abrahamic religion (see also, Judeo-Christian). The name "Christian" , meaning "belonging to Christ" or "partisan of Christ", was first applied to the disciples in Antioch, as recorded in Acts 11:26. The earliest recorded use of the term "Christianity" is by Ignatius of Antioch.

A religion is a set of beliefs and practices generally held by a community, involving adherence to codified beliefs and rituals and study of ancestral or cultural traditions, writings, history, and mythology, as well as personal faith and mystic experience. The term "religion" refers to both the personal practices related to communal faith and to group rituals and communication stemming from shared conviction.

All patriarchal 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".

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 (see religion-supporting organization). Other religions believe in personal revelation and responsibility. "Religion" is sometimes used interchangeably with "faith" or "belief system," but is more socially defined than that of personal convictions.