Religions, denominations, sects, and cults
Before we begin describing the individual religions, we need to be clear on a few general terms. "Religion", "denomination", "sect", "cult" - these terms do not have commonly agreed upon meanings. The best we can do when using them is to define what we mean before hand, so let me do that here.
I will use the definition already in use in the other books of this series for "religion". Religion is "the study and/or practice of what is generally considered to be religion - personal or organized." (From Theology 1: Philosophy of Religion - What is religion?). An adherent is a person who accepts the basic tenants of a religion. Every adherent has a slightly (or much more than slightly) different take on their religion and that makes for a great deal of complexity when talking about specific religions. For instance, I can say that all Catholics believe that the wine of the Eucharist is changed into the blood of Christ but I'm sure that a Catholic can be found that doesn't believe this. Just keep in mind that, when I talk about religions, I am overgeneralizing by necessity and am sticking to the main "party line" while describing some (but by no means all) major variations.
An orthodox belief is a belief that is supported by the primary tradition of a religion. A heterodox belief is one that is not. A heresy is a heterodoxy that is condemned by the authoritative clergy of a religion.
The word "creed" is derived from the Latin "credo" which means "I believe". A creed, then, is an authoritative statement of the central beliefs in a religion. A doctrine is a body of beliefs about a particular topic in a religion - particularly a collections of concepts which are actively taught within that religion. A dogma is a belief that is so established in a religion that it is accepted without question.
Almost all religions have variations that result from different interpretations of fundamental scriptures, traditions, or teachings. those variations are called "denominations". They are "spin-offs" of a parent religion. The term "sect" will apply to a denomination that is considered by the parent religion to be extreme or heretical but which becomes firmly established over time.
The term "cult" is difficult but important. It was originally a synonym of "denomination" but has evolved to have a darker usage. I do not want to use it in its most extreme sense of a dangerous or destructive body of religious beliefs but I will use it in its milder sense as a specific religion which is characterized by a central, authoritative, charismatic leader that exerts considerable power over the adherents of the religion.
Most of these definitions seem to be quite in line with what most people mean when they use the words. It's most important that you know what I mean when I use them.
The original religion among denominations may or may not exist currently but it can often be approximately described by original scriptures and by comparing commonalities among the denominations. For instance, much of Buddhism today is drastically different from the Buddha's original intention but there is a conceptual "core" Buddhism. Also, the range of variation in shamanism is vast but a core shamanism can be recognized by looking at the more "primitive" Siberian forms and by comparing the other forms.
The term "core" does not seem to be commonly used but it will come in handy here and I will use it occasionally. Also see it's use in the reference cited below.
Connelly, Paul (1996) Definition of Religion and Related Terms http://www.darc.org/connelly/religion1.html