My grammar book says that a word like "because" is a subordinating conjunction, meaning that it is a word that can introduce a dependent clause. I know that a dependent clause contains its own subject and predicate. For instance, this would be a principal clause and a dependent clause in which the dependent clause uses "because" and has its own subject and predicate:
"I went to the store [because I wanted those tomatoes.]"
However, I know very well that "because" could be used in other ways. For instance, we could say,
"I made this choice [because of you!]"
How would we label "because" in this case? It's only introducing a prepositional phrase. It's not introducing a subordinate/dependent clause with its own subject/predicate.