Prepositions are words that show the relationship between a noun or pronoun and another word in the sentence. They typically describe location, direction, time, or manner. Examples include:
* Location: in, on, under, beside
* Direction: to, from, towards, away from
* Time: at, before, after, during
* Manner: by, with, without
"But" is a conjunction, a word that joins words, phrases, or clauses. It is used to introduce a contrasting idea.
Here's an example:
* Incorrect: "I went to the store, but for milk." (Here, "but" is used as a preposition, which is incorrect.)
* Correct: "I went to the store, but I forgot to buy milk." (Here, "but" is used as a conjunction to connect two contrasting ideas.)