|Preach to the choir
|Crux of the matter
|Speak of the devil
|An act of faith
A sect is a collection of people adhering to a singular view within a larger scheme; in religion a sect is generally understood as a church or churches which have broken away from the larger church or denomination; religious sects often do not have a formal organizational body. Sects are generally understood as slightly if not totally heretical, at least from the position of the larger, formal body.
Most sects form when the prospective sect's founders disagree with their religion's established doctrine on many points, but the disagreement is not significant enough to warrant actually renouncing those beliefs. Some larger sects, such as The Church of Jesus Christ of Latter-Day Saints (a.k.a. Mormons), split (accustomed to distinctive fission) into subsects, such as (in this case) the LDS church, the Community of Christ, and smaller, moronic ones like the Kingston Clan and the Fundamentalist Mor(m)ons.
Religious syncretism can occasion the development of new sects in cases such as where a traditional religious system proselytizes amongst cultures with different worldviews and practices. Thus Catholicism in Northern Europe built on native traditions before morphing into Protestantism, European Christianity can give rise to new religious movements like the Taiping Rebellion in 19th-century China or to Antonianism in 18th-century Africa or to the Rātana Church in 20th-century New Zealand, and early Buddhism took on a distinct flavor after mixing with local beliefs and becoming Tibetan Buddhism.
There may or may not be base values
Some religions have no "base values" and are instead composed entirely of different and competing sects. For example, there is no generic Islam - you are either Sunni, Shia, or a member of another Islamic sect. Other religions, such as Christianity, have texts that are so ambiguous that they can be interpreted to mean anything, so that each individual congregation could be considered a sect in its own right, but even so there is a generic "non-denominational" designation for those who do not wish to commit themselves to any specific belief system. Catholicism and Protestantism are often so at war with each other you'd think they're different religions and interpretations but they are actually the same, only the method of worship (and generally the degree of how seriously and literally you take the Bible) are actually different. They are often included together in religion statistics under the generic term of "Christianity".
- Apostasy - Fully renouncing a religion.
- Heresy - What it's called when your new sect isn't big enough to defend itself.