Prepositions show the relationship between a noun or pronoun and another word in the sentence. They often indicate location, time, or direction. Here are some examples of prepositions:
* on the table
* at the store
* before dinner
* during the movie
"Minus" doesn't show a relationship in that way. It signifies the action of subtraction.
For example:
* 10 minus 5 equals 5.
Here, "minus" is the mathematical operation, not a word that describes the relationship between 10 and 5.