GS Grammar Guide: How & When to Use Commas

Commas are pesky little things with lots of different rules. This handy guide should help you figure out how to use them like a pro.

Commas are fickle creatures. It seems like they can't ever quite decide exactly where they want to go in a sentence. Sometimes, the grammar rules for commas are kind of arbitrary, which can make them really confusing for writers.

But never fear! This guide is going to help you out. Below you'll find the most common rules for using commas, a few weird rules, and extra tips on how to avoid comma mistakes when you're unsure. 

Rule 1: Use Commas to Separate Parts of a List

Ex. Do you prefer to play on PS4, Xbox One, 3DS, or PC?

Most people know this particular rule. Commas are always used when listing off things in a series. There is debate, however, over whether or not the Oxford comma is necessary - that's the comma that separates the the next-to-last item in the list from the conjuction that follows (in this case, "or").

It's not technically wrong to leave out the Oxford comma, but be aware that omitting it can create some confusion for your reader. Without the Oxford comma, the last two items in your list may get grouped together. 

Here's a great example of the value of an Oxford comma:

On first glance, your reader may think that you had eggs and toast together as one item or JFK and Stalin might be strippers. While this may seem like a small detail, a moment of confusion can jar your reader and pull them out of your article. So it's important to make sure your writing is clear. 

Rule 2: Use Commas Alongside Conjuctions to Connect Independent Clauses

Ex. My internet connection is slow, so my game is lagging. 

This is where comma rules start to get a little technical. In case you're unsure, an independent clause is any group of words that can stand on its own and make a complete sentence. (This is the opposite of a dependent clause, which is a phrase that must be attached to an independent clause in order to make a complete thought.)

conjunction connects phrases or clauses. Coordinating conjunctions connect two independent clauses, while subordinating conjuctions connect independent clauses to dependent clauses. The most common coordinating conjunctions are for, and, nor, but, or, yet, & so. 

When you're using a coordinating conjunction to connect two independent clauses, you must always have a comma BEFORE the conjunction. It's a common mistake to put the comma after the conjunction, but there are only a few rare cases where that would be necessary. 

Rule 3: Use Commas to Separate Introductory Phrases

Ex.  Before I can play this game, I need to update my system.

This is an important rule that writers often overlook. Because we hear our natural speech patterns in our heads when we read, and we know how a sentence is supposed to sound, we often forget that our readers need cues to see where we want those pauses to be. That's what the comma does in this case. 

When there is a phrase (dependent clause) in your sentence that cannot stand alone, it must be separated from the main part of your sentence with a comma. 

If your introductory phrase is only a word or two long, you can usually omit the comma without confusion. 

 Yesterday afternoon we played several rounds of Super Smash Bros.

If you're ever unsure about whether or not you can omit the comma after an introductory phrase, go ahead and use the comma, because it will always be correct (as long as it's appropriately placed at the end of the dependent clause). 

Rule 4: Use Commas to Separate Adjectives

Ex. Dark Souls II is an intense, grueling video game. 

Sometimes one adjective just isn't enough. When using more than one adjective to describe one thing, put commas between one adjective and the next. (But do not put commas before your first adjective or after your last adjective.) 

There are some cases in which commas aren't necessary between adjectives. The phrase "little old lady" is an example of this. But how do you distinguish when to use commas and when to leave them out? It's easy. If you put "and" or "but" between the adjectives and the sentence still reads well, then you use commas. If it doesn't sound quite right, that means you should probably leave the commas out. 

Dark Souls II is an intense and grueling game. 

vs.

The little and old lady crossed the street. 

See how that second one doesn't read smoothly with the conjunction in there? That's a sign that the comma isn't necessary. 

Rule 5: Use Commas around Interjections and Parenthetical Phrases. 

Ex. World of Warcraft, which is one of the most successful MMOs of all time, recently celebrated its ten-year anniversary. 

There are several parts to this particular rule, because there are a lot of different things that are considered parenthetical phrases. For some of you who may not know, a parenthetical phrase is any phrase (almost always contained in a set of commas) that you could remove from the sentence without changing its essential meaning. The example sentence above, for example, would still mean the same thing if we removed that middle part:

World of Warcraft recently celebrated its ten-year anniversary. 

We may have a little bit less information, but the point of the sentence still comes across. Think of parenthetical phrases as added or extra information. 

Whenever you have a parenthetical phrase, it must be enclosed in commas the way you would enclose something in parentheses. (Thus the term "parenthetical".)

Sometimes it's a little unclear what is and is not essential information. If you're really struggling with whether or not something is parenthetical, try restructuring the sentence to see if that gives you a better understanding of its parts. Sometimes a new structure is exactly what you need to really see into a sentence. And sometimes a new structure will simply read better. Don't think that just because you started a sentence one way, it has to stay that way. 

Here are a few examples of information that is always parenthetical:

1. Appositives are always parenthetical. An appositive is a re-naming of or elaboration on a word that immediately precedes it.

    • Example: My favorite gaming genre, the open-world RPG, is making a huge comeback.

2. Absolute phrases are always parenthetical. Absolute phrases consist of a noun/pronoun, a participle, and any modifiers. They do not modify a single word, but instead the whole sentence. Usually absolute phrases come at the beginning or end of a sentence, and should always be preceded or followed by a comma (or both), depending on its position. 

    • Example: The cosplayers, their costumes varied and elaborate, waited eagerly outside the convention.

3. Interjections are always parenthetical. An interjection is any word of phrase used to protest, command, or exclaim. Sometimes interjections (like "of course") are used more as flavoring words than essential parts of the sentence. Interjections are sometimes found alone, and sometimes containted within a larger sentence. Yes and no answers are considered interjections.

    • Example: Gaming requires a lot of skill, of course, and that's what makes it so rewarding.

4. An addressed person's name is always parenthetical. This is not to be confused with simply stating the name of the person being discussed, which would technically be an apppositive. If a person is being directly spoken to, his/her name will always be parenthetical. (The rules for appositive names are a little more flexible, and you can click this link for more info.)

    • Example: "I'm not kidding, Brian, we've been playing for 10 hours."

6. Use Commas to Introduce Quotes 

Ex. "We don't like to push back games," the developers said, "but we don't want to release a broken game either."

This is not something you'll use often, because we have that fancy little quote tool that visually separates quotes from other text. When attributing or introducing a quote, a comma must come after the introductory phrase and before the actual quote. If the attribution is in the middle of the quote (as above), it must be enclosed in commas. 

According to the developer's blog, "the patch will be released right after the holidays."

There is one exception to this rule. If you use the word "that" before the quote, you do not need to include a comma.

The developer stated that "they're doing everything they can to fix bugs as quickly as possible."

7. Use Commas to Separate Contrasting Phrases

Ex. I prefer to play Skyrim on PC, not console. 

This is probably one of the easiest comma rules. If you write a phrase that begins with the word "not", you'll almost definitely need to put a comma there. Contrasting phrases are a lot like parentheticals. They add information to the sentence, but the information is often not essential. If I were to remove the contrasting phrase in the above example, you'd still get the gist of the sentence. 

Be careful not to confuse this with using "not" as a modifier, as in this sentence:

I have not gotten a chance to play that game yet. 

That's Not All. Not By A Long Shot.

There are a lot of comma rules. Some of them are important and used often, like the ones listed above. Others are a little more obscure, and you'll hardly ever run into them. There are all kinds of technical rules about where commas go when dealing with the names of places, dates, etc. But we don't need to get into all those. (If you'd like to look over them, however, definitely do so.)

Perhaps the most important thing to remember with commas is that their purpose is to avoid confusion.

Commas help structure a sentence and give your readers visual cues that denote pauses, new phrases or information, quotations, or lists.

It's easy to overuse or underuse commas, and proper comma usage is a lot more complex than just "putting one where you'd pause in speech".

Hopefully this overview of comma rules will help you out in the future. And if you're still unsure about whether or not a comma is necessary, it usually helps to reorder the sentence so that you can better understand what elements you're working with. 

Commas are tricky, so don't get discouraged if it's difficult at first to distinguish when they're necessary. It takes a lot practice to recognize and really understand sentence structures. Think it out, do the best you can, and most of all, learn from your mistakes. If you do that, you'll be a comma master in no time. 

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Published Jan. 6th 2015

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