Much of comma use (particularly on the ACT) has to do with clauses. Remember that a clause is a group of words that contain a subject and a verb. Let’s review:
There are two types of clauses:
Independent clauses
Dependent clauses
An independent can stand alone as a sentence. In other words, an independent clause is really just a complete sentence.
One downside to the digital age is the disappearance of snow days.
This is a complete sentence. It has a subject-verb set (age-is) and includes all the words that go with the fact that “age-is.”
Dependent clauses still contain a subject and a verb, but they can’t stand alone as a sentence. This is usually because a word at the beginning of it means it has to be resolved in some way. See below.
Because the pandemic moved us in this direction…
Although we were headed there anyway…
After things settle down…
Each of these is a clause. They have a subject-verb set and all the words that go with them (pandemic-moved, we-were, and things-settle respectively). Note, however, that these clauses can’t stand alone because they don’t express complete thoughts. Each one needs something else (an independent clause) to resolve it, hence, each is a dependent clause.
Commas factor in two ways when joining clauses, and these represent a sizable chunk of the comma questions you’ll see on the ACT.
When you have a sentence that contains one dependent clause and one independent clause, a comma separates them ONLY if the dependent clause goes first.
Because the pandemic moved us in this direction, many students have said goodbye to snow days forever.
Here, the dependent clause goes first. Because the dependent clause comes first, a comma should separate the dependent clause from the independent clause that comes after it. Lastly, note that what comes after the comma here is a complete sentence, an independent clause.
If we rearranged it to put the independent clause first, we would not use a comma:
Many students have said goodbye to snow days forever because the pandemic moved us in this direction.
See how there was no comma between “forever” and “because”? That’s because, as we’ve discussed, when an independent clause comes first, you don’t use a comma.
Two independent clauses can also involve a comma, but not by themselves (see the chapter on [Comma splices]).
Two independent clauses can be joined by a comma and a coordinating conjunction, better known as the FANBOYS (For, And, Nor, But, Or, Yet, So).
Let’s look at these two independent clauses.
Independent Clause 1: I know I complain too much.
Independent Clause 2: We never get snow days, anyway.
If we wanted to join these with a comma + FANBOYS the sentence would look something like this:
I know I complain too much, but we never get snow days.
So there we have it. When used to join independent clauses, one way to do so is with a comma + FANBOYS.
These questions come up frequently on the ACT so make sure you have these rules on hand on test day.