When it comes to religion, there are many definitions of
what a religion is. Too many to count.
However, there are a few elements that most people agree are common to religions. Here's a short list of the most commonly mentioned ones in various sources:
1. Something Supernatural - Religions have some sort of supernatural explanation for things like the origins of the universe (cosmology) and what our fate is when we die (eschatology). Most religions also feature a supernatural deity or deities responsible for such things, but not all. Even the ones without deities, though, have a supernatural explanation of cosmology and eschatology. Those are basic questions that religions answer, correctly or erroneously.
2. Sacred Things - Sacred places, sacred things, sacred ideas, sacred shared symbols. Whatever. Stuff that is separate from the mundane world and must be honored in specific ways.
3. Rituals - Rituals are important. Some may be solitary practices, like prayer, while others require a group to carry out. For religions having a deity or deities, these rituals general involve supplications or obeisance to those.
4. Scripture - The information about the religion needs a context, so all can understand and follow the ideas expressed by the religion. This can be in written or oral form, although written scriptures exist for all major religions today.
5. Rules for Behavior - The concept of sin and righteousness or proper and improper actions is part of all religions I know about. Humans apparently need some sort of rules. If a religion doesn't supply them, the local culture will, or both. Religion provides a supernatural reward or punishment, generally for behaviors. It may also offer a special redemptive method for sin.
6. A Priesthood - Simple humans need religious leaders to keep them on track. Shamans, Pastors, Popes, Priests, etc. are part of all religions. These individuals conduct the rituals, counsel adherents, teach the religion and oversee things like death rituals, marriages, etc. These "priests" are believed by adherents to understand the religion fully and are supposed to be dedicated to it.
Those are the most common basic elements of religion. Lacking any of them, the religion doesn't exist. Other human associations also exist, but without all of the ingredients are not likely to be considered to be religions.
This is my list. I created it based on research into other people's lists. Your list may vary. But this is my list.
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