I am working on a conlang and have (for many months/years?) been perplexed by the prepositions. They standout because they are extremely hard to pinpoint what they actually mean, unlike a noun or verb, or even an adjective, and they are extremely hard to "visualize" to get a deeper sense of their meaning.
In the conlang, I had made the assumption early on that I am just going to treat every preposition like a "word modifier" (a "feature", really, in software/programming/modeling terms). That is, there are actions (verbs), objects (nouns), and features (properties), which are all standard / simple concepts to deal with in software / code. But prepositions are not easy to deal with, because they don't really have a clear meaning in my book. I mean, there are definitions of course, but they are often circular and/or imprecise, and rely on your intuition to fully understand.
For example, the word "from". Define "from".
indicating the point in space at which a journey, motion, or action starts.
Is that a noun then, a point in space? No, it's a preposition, it's like the relation between something and something else.
I walked from the rock to the tree.
So in my conlang, I initially followed my assumption and treated these prepositions as essentially "features" or "modifiers" of the corresponding objects or actions. So in this case, I would say "I walked (action, in past) [feature](position(start: rock, end: tree))". Or I don't know if that makes any sense, maybe "from (starts modification chain, with feature of distance being traversed, piping into the) the (sets focus on the upcoming object) rock ..." So really, "from" is a feature scope which is passed to the next feature which is "the", which is then passed to the noun "rock". That is, it is like an adjective, modifying the noun! So in my conlang, "from" is a feature which creates a new mental scope of what is to follow, signifying a movement in space. That is, "from" modifies the noun! It puts the noun (rock) into the animation of moving in space. It is a noun modifier.
Why doesn't that reasoning hold or work? What is wrong with the picture? Why can't I treat prepositions as adjectives (beyond just saying, "well this is how academia has said it should be")?
I feel like I can form perfectly good sentences by treating prepositions simply as noun/verb modifiers, but I'm not 100% sure yet. I won't go into any real detail in the conlang (will save that for the Conlang SE), but I will show a tiny piece to demonstrate the point. Haven't really gotten that far in advanced sentence construction. My sentences look a lot like English (placing the "feature" words like "fromo" (meaning "from + o" where "o" is a modifier suffix) into the same spot as they appear in an English sentence).
self-a walk-i past-o from-o the-o rock-a.
Where -a is a noun suffix, -i is a verb suffix, and -o is a feature suffix.