When to use a comma before “so”. Comma usage can be tricky. The word “so” follows a comma in certain instances. At other times, a comma does not appear before “so.” The type of clause employed after “so” determines comma usage.
Two types of clauses exist: independent and dependent. When you write an independent clause after “so” it is necessary to place a comma before “so.” Dependent clauses that follow the word “so” do not need a comma.
When to Use a Comma Before “So”
“So” + an independent clause = a comma
What is an independent clause? A clause that is independent can stand alone as its own sentence. An independent clause verbalizes a whole thought.
Independent clause example
- I love my brother, but I hate his haircut.
In this example, the coordinating conjunction “but” combines two independent clauses. Each independent clause can produce its own sentence.
Breaking down independent clauses into sentences
- I love my brother.
- I hate his hair cut.
In the above example, both independent clauses form their own complete thought. You can rewrite a sentence with two independent clauses into two shorter sentences.
Examples of “so” joining independent clauses
Seven coordinating conjunctions exist. “So” is one of these coordinating conjunctions. Nor, yet, or, and, for, and but are the remaining coordinating conjunctions. A coordinating conjunction like “so” joins two independent clauses and precedes a comma
- The store was out of broth, so I stole some from the guy next door.
- Frank had the lowest mark in language arts, so he received a tutor.
A comma appears before “so” because “so” joins two independent thoughts.
“So” + Dependent Clause
“So” can act like a coordinating or subordinating conjunction. That is to say, “so” can connect a dependent clause to an independent clause.
What is a dependent clause? A dependent clause is part of a sentence. It provides extra information to the sentence, but it does not convey a complete thought.
Example of a dependent clause
- The dog ate grass so he could turn green.
- She cleaned her room so she could go to the party.
In the first sentence the dependent clause “so he could turn green” does not indicate a full thought. “So she could go to the party” in the second sentence does not either. In both sentences, you want more information. You need to know what she had to do to go to the party or what the dog had to accomplish to turn green.
Determining if the clause is independent or dependent
Replace “so” with “therefore” in your sentence. If “therefore” works instead of “so” then “so” works as a coordinating conjunction. In this case, you will need a comma before “so.”
Replacing a coordinating conjunction
- Frank had the lowest mark in language arts, therefore he received a tutor.
In this sentence “therefore” replaces “so” without changing the meaning. Hence, “so” acts as a coordinating conjunction.
Replacing a subordinating conjunction
Try replacing “so” with “so that” in a sentence. If “so that” works in the sentence “so” is being employed as a subordinating conjunction.
- She cleaned her room so that she could go to the party.
“So that” works as a subordinating conjunction in the example above because it can replace “so”.