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A quick ‘n easy (but non-exhaustive) guide to comma use

By Stuie Borenovich, Peer Writing Assistant

Today, I’d like to discuss comma use and its many intricacies, pitfalls, and, yes, even shortcomings. If you’ve ever written an essay or any extended piece of writing, you’ve probably, at some point, scratched your head and wondered where to include the commas in your sentences (if at all). In this blog, I’m here to clear up some of these issues with comma use, while simultaneously using an unfortunate number of commas myself.

In a List

The first and easiest rule for comma use concerns lists: separate all items in a list with a comma, as in the following example:

     The countries that comprise the United Kingdom are England, Scotland, Wales, and Northern Ireland.

Here, a comma separates each of the countries in the list. Now, some of you may have noticed that I chose to include a comma before the “and” joining the second last and last item of the list; this comma is known as the Oxford comma or serial comma. The Oxford comma is often considered optional, but it can add clarity to a list, as we see below:

     I would like to thank my parents, Ayn Rand and God.


     I would like to thank my parents, Ayn Rand, and God.

In the first example, the reader might infer that the writer’s parents are Ayn Rand and God rather than two unrelated, possibly non-parental figures. In the second example, the Oxford comma provides clarity and eliminates any ambiguity. However, inserting a final comma before the last item in a list does not always make things more understandable. Case in point:

    I had coffee with Gavin, my friend and my roommate.


    I had coffee with Gavin, my friend, and my roommate.

In the first example, it is unclear whether Gavin is my friend and roommate or whether I am having coffee with three different people. Even with the addition of the final comma in the second example, it remains unclear as to whether there are three people or simply two and Gavin is also my friend. The choice to use the final comma is then a stylistic one and depends on the preference of the writer; regardless, you should use or not use Oxford commas consistently throughout a work.

After Introductory Phrases

The most tedious use of commas may occur when off-setting introductory words or phrases. Prior to an independent clause, it is common to insert short precursors to a sentence:

     The Queen’s student wanted to sit on the chair. In opposition,
the cat regarded the student with no intention of vacating his territory.

In this example, the phrase “in opposition” acts as an introductory phrase to the independent clause and is thus offset by a comma. Other examples of introductory words are “however,” “conversely,” “meanwhile,” “therefore,” etc. This rule mostly requires close attention to your writing and an understanding of what you are trying to say in determining where the introductory phrase differs from the main part of your sentence.

To Introduce Non-restrictive Appositives

Another instance that requires a comma is in the use of non-restrictive appositives, a term that is basically just a fancy way of saying you’ve renamed something after you’ve mentioned it:

     I took my dachshund, Weiner, for a walk today.

The appositive here is “Weiner” (the name of my dog). This additional information is unnecessary for the clarity of the sentence, however, and so we offset it with commas. If I had two dachshunds, the appositive would become restrictive, and I would no longer be able to offset my dog’s name, as we see in the following example:

     I took my dachshund Weiner for a walk today while his brother was at the vet.

To Link Clauses

Finally, use a comma to link two clauses. Before we get to the commas, though, let’s make sure we’re clear as to the two types of clauses: dependent and independent. Simply put, an independent clause is a phrase that has a subject and a verb and can stand alone as a sentence; a dependent clause also has both a subject and a verb, but cannot stand alone.

     While I was out for a jog, I noticed the leaves had started to change colour.

The first part of the sentence, “while I was out for a jog,” is a dependent clause because it cannot be a complete sentence on its own. Conversely, “I noticed the leaves had started to change colour” is an independent clause and can stand as a sentence. You will notice I have joined the clauses with a comma. A sentence can also be made up of two independent clauses as well, which requires a comma.

     The quick dog was brown, and he jumped over the lazy fox.

In the sentence above, both “the quick dog was brown” and “he jumped over the lazy fox” can be independent sentences, which means the clauses need to be joined by a comma. I have also included “and” in this sentence, though, because, when joining two independent clauses, one of the clauses requires one of seven coordinating conjunctions (and, but, or, nor, for, yet, so). Failing to include a coordinating conjunction in this situation would result in a comma splice, which is a major grammatical fault.

 That’s all there is to it! Here’s hoping this short guide will help you avoid comma-related confusion while editing your essays!