Grammar: Commas before conjunctions and complete thoughts

Since we’re probably all still recovering from the last few days of heavy eating and shopping, I thought I’d keep this month’s topic short and sweet: using commas before conjunctions when they are followed by a complete thought.

Let’s break that down.

First: conjunctions.

You may remember conjunctions from School House Rock: “Conjunction junction, what’s your function?” Basically, a conjunction is a joining word, something that connects sentences or phrases. Common conjunctions include “for,” “and,” “not,” “but,” “or,” “yet,”  and “so.” (Making the acronym FANBOYS…)

Second: a complete thought.

A complete thought is one that contains, at a minimum, a subject and a verb. (Also known as an independent clause.)

EXAMPLE: “The cow jumped over the moon.”

The subject is “cow,” the verb is “jumped.”

So we know what a conjunction is, and we know what a complete thought is. Now, where does the comma fit into this?

If you have two complete thoughts joined by a conjunction, you should put a comma before the conjunction. This comma is important because it is a visible clue to your readers that they can pause between the two parts of the sentence. It improves your readability.

Examples of commas before conjunctions:

EXAMPLE: “I don’t appreciate your tone, and I don’t appreciate that look on your face,” she said.

First, find the conjunction: “and.” Then look at what comes before and after the conjunction: “I don’t appreciate your tone” and “I don’t appreciate that look on your face.” Both of these are complete thoughts because they have a subject and a verb (“I” and “appreciate” for both.)

EXAMPLE: She hated his beard but not his mustache.

The conjunction is “but.” But if we look at what comes before and after the conjunction, what do we see? “She hated his beard” is a complete thought. But what about “not his mustache”? Do we have a subject and verb there? No! We do not! Therefore, you do not need a comma with that particular conjunction.

So remember: use commas before conjunctions when the conjunction is joining two complete thoughts to help your reader find the natural pause in your sentence. Your writing will be easier to read, which means your readers can stay sucked into your story. And don’t we all want that?

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Rachel is a full-on, hardcore grammar freak. Her favorite punctuation marks are parentheses, em dashes, and ellipses. She still loves adverbs but is trying to wean herself off of them. And she truly believes that it’s okay to split an infinitive. In addition to her grammar obsession, Rachel writes light contemporary romance – occasionally with a paranormal twist – and is published in short fiction. Check out her other grammar tips here.