Grammar Minute – And a Comma?

One of the most common punctuation errors I see in writing is misusing commas around conjunctions. Luckily, once you know what to look for, it becomes easier to determine whether or not a comma should be included.

First, when should you use a comma?
If the sentence could be broken up into two full sentences instead of using the conjunction, use a comma.
If there is a list of 3 (phrases, objects, clauses, etc.), I recommend using a comma (this is a serial/oxford comma).
If the phrase after the conjunction refers back to an earlier part of the sentence, do NOT use a comma.

There are exceptions to every rule, and the more complex your sentences are, the more likely it is that there will be multiple rules at play. Let’s start with the basics, and it’ll get easier to add in other rules once this one feels natural. 

Here’s my trick: read the second half of the sentence as though it’s its own sentence. If the meaning changes OR it’s not a complete sentence, don’t include a comma.


We’ll go to dinner after I finish packing and you load the car.“You load the car” is a complete sentence, but it refers back to “after,” so no comma is needed.
Steve likes to sleep, and I like to read when I should be sleeping.These are two independent clauses (complete sentences), so a comma is needed.
She called the restaurant but didn’t make a reservation.“But didn’t make a reservation” is not a complete sentence (it has no subject), so no comma is needed.
They were understandably upset, but there was nothing they could do about it.These are two independent clauses, so a comma is needed.
Olivia sang, Piper played the guitar, and the rest of them danced.These are three independent clauses, so commas are needed.
They swam in the ocean, played in the sand, and lay in the sun.This is a list of 3 dependent clauses, so the comma before “and” is a serial/Oxford comma*. 
She greeted Cynthia, who was wearing a red shirt, and asked her about her latest project.Here’s an example of when multiple rules are at play! The comma before “and” is offsetting the phrase “who was wearing a red shirt” and is unrelated to the conjunction “and.” If the offset phrase wasn’t there, then no comma would be needed before “and.”

*I always prefer using an Oxford comma, but when the list items are phrases, I would recommend using a comma even if you don’t generally use Oxford commas, because it helps with readability.

The hardest part of applying this to your writing is that if you’ve been using them incorrectly, commas will look wrong to you even when they are applied correctly. Keep fixing them until they start to look right. And remember that a comma in writing doesn’t necessarily mean a pause in speaking, so you can add a comma even when you wouldn’t slow down while reading that line out loud.

Your “homework”:

  1. Pick one (unedited) chapter to check. 
  2. Read through looking for conjunctions (and, but, or, so, etc.).
  3. For each conjunction you find, break the sentence up into two sentences at the conjunction to determine if you could have two grammatically correct standalone sentences without changing the meaning. If so, include a comma! If not, keep it out.
  4. If you find a sentence you’re not sure about, send it my way! I’d love to help you figure it out.
  5. Enjoy the feeling of knowing your book is even better than it was before!

Paige K

What are your grammar hang-ups? Let me know, and you may see them featured in future blog posts.

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