What is a Subordinating Conjunction

Grockit is an online test prep and collaborative learning tool that allows students to practice tests in the three ways they naturally study – alone, with peers, and with experts. This guest blog was written by Jordan Schonig, a writer for Grockit.
As a continuation of our discussion on how to properly use conjunctions, we are now going to take a look at the subordinating conjunction.
Like coordinating conjunctions, subordinating conjunctions help to connect two independent clauses, but they can only do so by making one of the clauses dependent (i.e. subordinate). When I place a subordinating conjunction in front of an independent clause, I render that clause dependent, thereby facilitating its linkage with an independent clause.
Examples of subordinating conjunctions are: Because, before, after, when, since, until, although, while.
Comma use with subordinating conjunctions depends on the placement of the clauses:

  1. When the independent clause comes first, you don’t need a comma.
  2. When the dependent clause comes first, you need a comma to separate the clauses.

Here are some examples of this difference:

  1. Because I forgot to study, I received a failing grade on the exam.
  2. I received a failing grade on the exam because I forgot to study.

Notice that each sentence has two clauses, one of them independent and the other dependent. The clause “because I forgot to study” is dependent; it cannot stand alone as a sentence. If we were to remove “because,” though, “I forgot to study” would function as an independent clause. The subordinating conjunction renders the clause dependent.
A common error is placing a comma before the subordinating conjunction in the second form:
“I received a failing grade on the exam, because I forgot to study.”
This is wrong. You do not need a comma when you place the dependent clause after the independent clause. As you can see, conjunctions are accompanied by specific comma rules. As you all know, these tests, especially the ACT, love to test for comma usage, so beware of comma placement when you see conjunctions like these.
Don’t forget to read about What is a Coordinating Conjunction.