The nonjudgmental term of art appears to be "adposition". It isn't clear to me why this was coined as "adposition" and not "apposition".
"Preposition" is already something of an unnatural word class. They have two main functions in English: to describe some kind of location ("Sam? He's with Natasha"), and to mark certain arguments to verbs ("The tools? Sam's playing with them").
It's just a coincidence that prepositions serve both of these purposes in English; in Mandarin, the same two purposes are served by completely separate word classes. Verb argument markers are preposed; location markers are postposed.