Commas are one of the most commonly used punctuation tools. Sadly, they are also one of the most misused. You may come across writing littered with stray commas or you may encounter writers who who simply omit the punctuation, creating wildly confusing sentences that have no breaks in sight.
You may have been taught to use a comma when the reader would naturally pause or need to take a breath. Unfortunately, in the rules of grammar it's not quite that simple.
There is in fact an explicit set of grammar rules that governs the use of commas. But those rules can vary from style guide to style guide, creating an even more confusing mess for many writers. So we're here to break down some of the more useful rules in an attempt to end the plight of the comma.
Rule number 1: Lists.
Let’s start with an easy one. Commas are used when writing lists of three or more items.
Example 1: I’m going to the store to buy flour, sugar, eggs, and jellybeans so I can make a jellybean cake.
Sound simple? Well, it's a bit more complicated than that. That last comma in the series (the one after the word "eggs") is called the Oxford, or serial, comma, and it's optional depending on who you ask.
Some style guides, like Chicago, include the comma. But you'll find other style guides like AP Style (used primarily in journalism) eschew this rule, leaving out that final comma and writing the sentence as such: I’m going to the store to buy flour, sugar, eggs and jellybeans so I can make a jellybean cake.
If you're just typing an email to a colleague or posting on a personal blog, you can decide for yourself whether you want to include the comma or not. But if you're publishing in a professional setting, do a little research on which style guide fits your audience.
Rule number 2: Linking independent clauses.
Independent clauses are fully-formed ideas that could stand alone as sentences. When they are joined together with a conjunction (and, or, but, etc.), they need a comma.
Example 2 (the two independent clauses are bolded): I baked a jellybean cake, and it tasted better than I could have imagined.
In this case, the two independent clauses could each be its own sentence. But because they are combined, and linked by the word "and", they need a comma to separate them.
Rule number 3: Dependent clauses.
Dependent clauses feature a subject and a verb, but aren’t complete sentences on their own. They tend to add a little contextual spice to an otherwise bland statement. If your sentence attaches a dependent clause to its independent counterpart, the two are joined with a comma.
Example 3 (the dependent clause is bolded): When I have a bad day, I comfort myself with a slice of jellybean cake.
Rule number 4: Non-essential descriptions.
Captivating writing often adds further details to bring a sentence to life. But if you can remove the phrase without it changing the sentence, it's considered non-essential. No matter where they appear in the sentence, these descriptive, words or phrases need to be shielded with commas.
Example 4 (the non-essential phrase is bolded): The jellybean cake, sweet and chewy, was the perfect dessert.
Rule number 5: Quotations.
When someone is speaking or being quoted, a comma needs to precede or follow the speech. Depending on the order of the sentence, the comma can be inside or outside of the quotation marks.
Example 5: “This jellybean cake is simply sublime,” gushed the Michelin-starred chef.
The waitress said, "I agree, it was truly delicious."
Rule number 6: Introductory elements.
Introducing a sentence with an adverb (ex. unfortunately, interestingly), or joining words and phrases (ex. on the other hand, furthermore), require a comma.
Example 6: Unsurprisingly, jellybean cake is about to take the world by storm.
Rule number 7: Addresses
Streets, cities, states, and countries need to be separated with commas when writing addresses.
Example 7: The Jellybean Cake Corporation international headquarters are located at 123 Cake St, Candyland, FL, USA.
Rule number 8: Dates
Like addresses, the day, month and year in a date need to be punctuated with commas.
Example 8: Legend has it, the concept of the jellybean cake was conceived on Thursday, April 20, 1574, by Spanish explorers.