A subordinate clause, also known as a dependent clause, begins with either a subordinating conjunction or a relative pronoun. Despite containing both a subject and a verb, a subordinate clause cannot stand on its own as a sentence. It requires additional information in order to complete the thought expressed in the subordinate clause. A subordinate/dependent clause is subordinate to/dependent upon an independent clause.
Common Subordinating Conjunctions and Relative Pronouns
Subordinate clauses always begin with subordinate conjunctions or relative pronouns. Common subordination conjunctions include: after, although, as, because, before, even if, even though, if, in order that, once, provided that, rather than, since, so that, than, though, unless, until, when, whenever, where, whereas, wherever, whether, while, and why. Relative pronouns are: that, which, whichever, who, whoever, whom, whose, whosever, and whomever. Seeing one of these words indicates that you are dealing with a subordinate clause.
Subordinate Clause Examples
Take a look at the examples below. Each one contains both a noun and a verb but also implies a question. That “question” needs to be answered with an independent clause.
After Ben went to the bank…
What happened after Ben went to the bank?
Once Emily finished the report…
Emily has finished the report? Now what?
Until Mira began taking classes at the English Island in Atlanta…
What was the state of Mira’s English language skills before she began taking classes?
Who recommended her to the English Island…
Who, exactly, gave the recommendation?
Remember: A subordinate clause must always be joined with an independent clause. This is true even when, as in the first two examples, the clause would form a simple sentence if you removed the subordinating conjunction. The addition of a subordinating conjunction transforms a phrase that has the potential to be an independent clause into a dependent one.
Correct and Incorrect Subordinate Clause Usage
When you place a subordinate clause before the main clause, the clauses should be separated by a comma:
After Ben went to the bank, he drove to the grocery store.
Once Emily finished the report, Eric checked it for errors.
No comma is used when the subordinate clause comes after the main clause:
Mira struggled to learn English until she began taking classes at the English Island in Atlanta.
Mira’s coworker is the one who recommended her to the English Island.
Essential and Non-Essential Relative Clauses
When a subordinate clause begins with a relative pronoun, you will sometimes need to break the “no comma if the clause comes at the end” rule. Whether or not you need a comma is determined by whether or not the clause contains information that is essential to the meaning of the sentence.
When the main clause includes only a general noun (tutors), the information in the relative clause is considered essential to the meaning of the sentence. In this case no comma is used:
Carl recommended Mira take classes from one of the English Island tutors who had helped him to improve his own English skills immensely.
If, on the other hand, we swap out “tutors” for the name of a specific person, the relative clause is no longer essential to the meaning of the sentence. Now the comma is necessary because the clause only serves to provide additional information:
Carl recommended Mira take classes from Joe, who had helped him to improve his own English skills immensely.
Relative clauses can also interrupt main clauses. The rules for this are similar to those discussed above: When the clause contains essential information, begin the clause with a comma but do not end it with one. When the clause does not contain essential information, frame the entire clause with commas.
Essential interrupting relative clause (generic noun):
After running to the bank, the man who was on his lunch break returned to the office.
If you remove “the man who was on his lunch break” from this example, you wind up with a sentence fragment.
Non-essential interrupting relative clause (specific noun):
After running to the bank, Ben, who was on his lunch break, returned to the office.
You can safely remove “who was on his lunch break” from this sentence without converting it to a sentence fragment.