Subordinating conjunctions, also called subordinators, are conjunctions that join an independent clause and a dependent clause, and also introduce adverb clauses. The most common subordinating conjunctions in the English language include after, although, as, as far as, as if, as long as, as soon as, as though, because, before, even if, even though, every time, if, in order that, since, so, so that, than, though, unless, until, when, whenever, where, whereas, wherever, and while.
Complementizers can be considered to be special subordinating conjunctions that introduce complement clauses: e.g. "I wonder whether he'll be late. I hope that he'll be on time". Some subordinating conjunctions (until and while), when used to introduce a phrase instead of a full clause, become prepositions with identical meanings.
The subordinating conjunction performs two important functions within a sentence: illustrating the importance of the independent clause and providing a transition between two ideas in the same sentence by indicating a time, place, or cause and therefore effecting the relationship between the clauses.[8]