A religious denomination is a subgroup within a religion that operates under a common name, tradition and identity.
The term describes various Christian denominations (for example, Eastern Orthodox, Catholicism, and the many varieties of Protestantism or Restorationism). The term also describes the four branches of Judaism (Orthodox, Conservative, Reform and Reconstructionist), and describes the two main branches of Islam (Sunni and Shia).
In Hinduism, the major deity or philosophical belief identifies a denomination, which also typically has distinct cultural and religious practices. The major denominations include Shaivism, Shaktism, Vaishnavism, Smartism and Halumatha.
Another example is the Lutheran Church. When Martin Luther protested Catholic practices, he and his followers were persecuted by the Roman Catholic Church as heretics. This led to the formation of alternative communities of practice that became known as "Lutheran" or "Protestant." Over time, the various churches who considered themselves Lutheran identified with one another and through various definitions of "Lutheran" practices (Heidelberg Catechism, five solas, priesthood of all believers) the conglomerations of churches formed concrete denominations based on a common school of thought related to these practices. Even today, there are major ideological differences between different denominations of Lutherans, although there may be significant overlap between their beliefs.