Comma Before or After So | Rules & Examples
- When “so” could be replaced with “therefore,” use a comma before “so.”
- When “so” could be replaced by “so that,” don’t add a comma.
|“So” meaning “therefore” (comma)||“So” meaning “so that” (no comma)|
|I was hungry, so I ate some chips.||Maria is saving up so she can move out.|
|I was hungry. Therefore, I ate some chips.||Maria is saving up so that she can move out.|
“So” meaning “therefore”: Use a comma
When “so” is used to mean “therefore” (or “for that reason” or “because of that”), it’s classed as a coordinating conjunction connecting two independent clauses. When coordinating conjunctions (e.g., “so,” “and”) connect independent clauses, a comma is always needed.
If you’re not sure whether “so” is functioning in this way, try replacing it with “therefore” and “so that” to see which one better fits your meaning. For example, consider the sentence “He told me to let you know, so I’m passing on the message.”
Replacing “so” with “so that” results in a sentence that doesn’t really make sense:
- He told me to let you know so that I’m passing on the message.
But replacing “so” with “therefore” conveys the meaning correctly (though with a more formal tone):
- He told me to let you know. Therefore, I’m passing on the message.
Based on this, we can conclude that “so” is functioning as a coordinating conjunction and that we need the comma before it.
“So” meaning “so that”: No comma
When “so” is used as a synonym of “so that” (or “in order that”) it’s instead classed as a subordinating conjunction. A subordinating conjunction connects an independent clause with a dependent clause (a clause that can’t stand on its own as a complete sentence).
When it’s used in this way, there should be no comma before “so.” Again, a good test is to try replacing “so” with “therefore” and “so that” to see which one matches your intended meaning. For example, take the sentence “I ducked so I could pass under the branches.”
Replacing “so” with “therefore” results in a statement that makes sense but is unlikely to be the intended meaning:
- I ducked. Therefore, I could pass under the branches.
Using “so that” instead results in a statement that matches the original in meaning:
- I ducked so that I could pass under the branches.
Therefore, “so” is functioning as a subordinating conjunction, and no comma is needed. Note that it’s normally better to write “so that” in full in academic writing—both because it removes potential ambiguity and because it’s considered more formal.
Is there ever a comma after “so”?
There’s normally no need for a comma after “so,” whether it’s used as a coordinating or subordinating conjunction. Like other conjunctions, it’s just immediately followed by the clause it introduces.
Many people add a comma after “so” when it appears at the start of a sentence. This is not necessary when “so” functions as a conjunction; it’s better to leave out the comma:
- I needed some milk. So, I ran down to the store.
- I needed some milk. So I ran down to the store.
When “so” is used as a meaningless interjection, as is common in everyday speech, you can add a comma or not, depending on whether there’s a natural pause at that point in the sentence:
- So, what do you think?
- So I’m going to head out now.
Note that you shouldn’t use “so” like this in academic writing, as it’s informal and doesn’t convey any clear meaning.
One other context where a comma may be needed after “so” is when it’s immediately followed by an interrupter: a phrase that interrupts the flow of the sentence to qualify or emphasize something. Interrupters are surrounded by commas.
Worksheet: Comma before or after “so”
Test your knowledge of when you need a comma before or after “so” by completing the worksheet below. Just add commas wherever you think they’re needed to the example sentences, and then check them against the answers provided.
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