An ideology is a set of one or more "beliefs" (what I call "modules"). I make a distinction between a monomodular (MM) ideology and a polymodular (PM) ideology. Examples of monomodular ideologies are atheism, polytheism and pantheism, which offer only one module. A follower of a monomodular ideology is someone who adheres to the module offered by that ideology. For example, and atheist is someone who thinks that nothing is divine, a polytheist is someone who thinks there are multiple divinities and a pantheist is someone who thinks everything is divine. A polymodular ideology offers multiple modules: examples of polymodular ideologies are Christianity, Islam, Psychiatry, Buddhism, Scientology, Pastafarianism, Laveyan Satanism, Marxism and National Socialism (a.k.a. Nazism) and many many others, of course I'm not gonna list all that exist. What is a follower of a polymodular ideology, that can be a can of worms, an object of intense discussion. Here are some approaches (I'll use Islam as an example because it's the polymodular ideology I'm most familiar with, so I can provide better examples) (oh, by the way, I make a distinction between "binary" and "fuzzy" approach... a binary approach is one that says one is either a follower or not a follower of a PM ideology, whereas a fuzzy approach allows degrees of in-between):
1 (binary approach): a follower of a PM ideology is one who adheres to all the modules offered by that ideology. If someone rejects even one module offered by that ideology, then that person is not a follower of that ideology.
2 (fuzzy approach): the higher the amount of modules adhered by a person, the more that person is a follower of that ideology. If someone adheres to all modules of a PM ideology, then that person is a full follower, if someone adheres to none of the modules, that person is fully a "non-follower", and there are many degrees of in-between.
2.1: Each module is of equal importance.
2.2: Modules can vary in importance, so certain modules affect the "score" (so to speak) of how much a person is a follower of a PM ideology much more than other less important modules.
3: (binary approach): modules are classified as either "essential" or "non-essential": a follower of a PM ideology is a person who adheres to all essential modules. For example, for Islam, essential modules may be the five pillars (Shahada, pilgrimage to Mecca, fasting during Ramadan, the charity thing, and the five daily prayers), so with this #3 approach, a Muslim is anyone who adheres to the five pillars of Islam, and therefore, someone who is pro-homosexuality, pro-sex before marriage, pro-polyamory (polygyny and polyandry), pro-alcohol, pro-marijuana etc. can still be considered a Muslim. But not someone who is pro-polytheism, because the Shahada is explicitly against that, since it explicitly says that the gods do not exist (except Allah). However, what is an essential module can be subjective and up to debate, so one can argue anti-homosexuality, anti-alcohol, anti-sex before marriage etc. are also essential modules of Islam.
3.1: A slight variation of this essential vs non-essential module approach is that one can still be considered a follower of a PM ideology if, say, s/he adheres to like 90% of essential modules, as long as that person "compensates" by also adhering to a very large amount/proportion of non-essential modules as well, which is something that can be considered to "fill the void" somehow.
4: (binary approach): a follower of a PM ideology is a person to adheres to at least 50% of the modules of that ideology. How each individual module is counted can be somewhat subjective, however. For example, it can be debated whether a module is one module or two modules etc. when it's a more complex sentence.
x: Other options may be coming soon.
IDEA: emergent modules! For instance, when thinking about atheism, some may think about "scientific rationalism" or "materialism" or something like that. This is merely a historical contigency, since atheism merely states that nothing is divine, that nothing can be considered a deity, (or that there are no gods, if you prefer that wording). "Scientific rationalism" is not a module contained within atheism, but it's an emergent module that arose from historical contingencies.
There may be different ways to categorize worldviews. One of those ways (a quite common one) is to regard worldviews as strictly defined packages that contain "beliefs" (which I call "modules"). A common approach is to say that a person can only be considered a "follower/adherent" of a certain worldview at a time (discouraging eclecticism and syncretism). What's more, it seems to often be the case that certain modules are associated with a certain "package" (worldview) and it is considered invalid (or perhaps quirky in a bad way) to adopt that module without adopting the entire package. For example, with this approach, it would be considered invalid for someone to fast during the month of Ramadan, if that person is a liberal panentheistic/polytheistic occultist who is very pro-LGBT, pro-polyamory and praises Prometheus, Satan, Sophia, Hedone, Lucifer and Jesus as the main deities of that person's pantheon, and yet decides to fast during the month of Ramadan. This is because fasting during the month of Ramadan is considered (in this approach) as a module that is exclusively found within the package called "Islam" and cannot be found in any other package. Someone who adopts the "package" approach I've described may say to such an eclectic person "bro, wtf is your religion, why...". This approach discourages eclecticism and syncretism, encouraging following well-defined packages instead. "It's all or nothing". An example of this approach that is common on certain corners of social media is to bundle certain (completely unrelated) attitudes together and call them "left-wing" or "right-wing", and then forcing oneself (and expecting other people) to adhere to the entire package. For example, someone who is pro-LGBT may force oneself to oppose gun ownership, to be pro-abortion, to support Ukraine, to support forced vaccinations, to be an atheist (usually, not always), and to adopt a vaguely corporate, rainbow aesthetics (I may create a page about the relationship between worldviews and aesthetics eventually... this is something rarely talked about). Even if someone does not agree with those ideas, they may adopt them because they're included in the package, and some people don't consider eclecticism as a valid option. This is what I call a "package-focused" approach.
But there are other possible approaches! A module-focused approach (as opposed to a package-focused approach) focuses on modules instead of packages. A person is not labelled or judged based on their adherence to packages, but their adherence to modules. This makes eclecticism a much smoother and intuitive experience. Simple labels are generally not used (e.g. "this person is a [insert worldview word -ist]") is less likely with the module-focused approach. One can say "this person is mostly/a bit/fully/not-at-all [insert worldview], but also mostly/a bit/fully/not-at-all [insert different worldview]", but the worldviews are understood as arbitrary packages of modules packaged in a certain way because of historical contigencies. There may be other approaches too, which I may list in the future.
Note: this is an observation of mine. There is no logical reason why things should be this way, though there is a psychological reason. If my understanding is correct, this phenomenon occurs due to a cognitive bias known as "negativity bias" (it may also be due to gods/ghosts/spirits/etc. if you prefer that).
Opponents of a certain worldview are more likely to apply the label (to others) far more loosely than prononents of said worldview, who tend to be far more strict in applying it. The more one opposes a worldview, the more loosely (as a general rule) one tends to apply that label. For instance, the subset of Christians and Muslims who are highly Exterian will call anything that even slightly deviates from their worldview "Satanic", whereas a Satanist (especially a Laveyan Satanist!) would use that term far more strictly, and thus, anything that slightly deviates from their worldview is "not at all Satanic". In the context of mainstream "political" discussions on social media, this phenomenon is very commonly observable as people who self-identify as "right-wing" calling anything they disagree with "woke" (or "far-left"), and people who self-identify as "left-wing" calling anything they disagree with "far-right". Thus, in the context of those conversations, anyone who does not display predictable and consistent patterns of "left-wing" or "right-wing" talking points will be considered "far-right" and "far-left" simultaneously, though of course by two distinct groups of people. For more information check my "Exterius" page.