Ontology is the study of being. Yeah, anyway, here are some ideas:
1: Monism: only one thing "exists".
2: Dualistic paradigm: existence vs non-existence. These terms are not further defined.
2.1: What is made of matter, what is not made of matter does not exist (so, light, gravity, temperature, time etc. do not exist)
2.2: What is made of matter as well as what interacts directly with matter exist, everything else does not exist (so, numbers, marriage, country borders, gods, morality, desires, nationalities, religions, philosophies, mathematics, geometry, the months of the year, the days of the week, temperature scales etc. do not exist)
2.3: only what is definitionally impossible does not exist (e.g. a square circle, a married bachelor etc.)
3: Dualistic paradigm: physical vs metaphysical (which means "beyond the physical").
3.1: Physical is defined as "what is made of matter", whereas metaphysical is something that is not made of matter. Examples of physical things: chairs, rocks, rivers, clouds, alcoholic beverages, mountains etc. metaphysical objects may include numbers, abstract concepts, country borders, consciousness, light, electromagnetic radiation in general, temperature and gravity.
3.2: Same as above except that what interacts directly with physical objects is also considered physical. So, unlike in 3.1, light, electromagnetic radiation in general, temperature and gravity are considered physical.
4: Same as 3.2. but what is considered metaphysical in 3.1 and physical in 3.2 (light, electromagnetic radiation, temperature and gravity) is considered "transphysical" here, so there are three ontological categories here: physical, transphysical and metaphysical
5: Sensorial vs non-sensorial. Sensorial is what is perceived by "the five senses", and non-sensorial is what is not. Examples of sensorial objects are: chairs, rocks, rivers, clouds, alcoholic beverages, mountains etc. whereas non-sensorial objects may include numbers, abstract concepts, country borders, non-visible electromagnetic radiaton etc. temperature may be considered sensorial because, even though it's not perceived by the common definitions of "the five senses", it is still sensorial because it is sensed by what is called "thermoception". In some interpretations, one can say that one senses temperature through touch, and so, it can be easily argued that temperature is sensorial. Light is more ambiguous, because one can either say that one senses light through the sense of sight, or that one does not sense light itself, but only the objects that are made visible by light. In any case, with my clever method, it's always possible to "solve" these problems. Look:
5.1: Light is sensorial because one can sense it through sight
5.2: Light is non-sensorial because what one senses through sight is not light itself, bur rather, the object(s) made visible by light.
This is how it's done, lmao
6: Ternary paradigm: concrete existence vs abstract existence vs non-existence (kinda similar to Meinongian ontology but not quite): the first two are quite self-explanatory, non-existence is stuff that is definitionally impossible (e.g. a triangle with four sides, or a married bachelor). Details:
6.1: What is not made of matter but interacts with it (e.g. gravity, temperature, electromagnetic radiation) etc. is considered concrete existence.
6.2: What is not made of matter but interacts with it is considered abstract existence.
6.3: (Quaternary paradigm? Well, depends on how you count it): abstract existence is further sub-divided in (for lack of better terms) "actual abstract existence" vs "potential abstract existence". Santa Claus is "actual abstract existence", since that concept is well-known throughout most of the word, whereas Santa Claus' brother, Robert Claus (which I made up myself) is not, so it's "potential abstract existence". These terms suck so I may try to find something better eventually. But until then... oh, and the distinction between actual vs potential abstract existence may be binary - in which case some concept is either one or the other, and an arbitrary line is drawn between the two, or fuzzy - in which case it's actually a spectrum between the two, depending on how "popular" the concept is.