So you’ve had a few months to think over, practice, and master the three comma rules I presented to you in April, and now it’s time to learn two more that will help you spruce up your writing while still satisfying those pesky grammarians.
USE A COMMA TO SET OFF A PARENTHETICAL or NONESSENTIAL ELEMENT
As you may remember from Sentence, INTERRUPTED! - Five Ways to Interrupt Yourself (Grammatically), commas can be used to set off material that is not grammatically or contextually required in a sentence. A good thing to note here is that, unless the nonessential clause comes at the end of the sentence, there needs to be a comma at the beginning AND at the end of the parenthetical section. The most common mistake that I see with this rule is that the writer forgets to put the comma at either the beginning or the end of the section. An easy way to remember it is to remind yourself that like parentheses, parenthetical commas come in pairs.
Parenthetical elements can be called “added information” and there are several different kinds. Here are four types that you should learn.
Appositives
An appositive, according to The Little, Brown Compact Handbook, Fifth Edition, “is usually a noun that renames another noun.” Appositives add information by modifying a noun that occurs elsewhere in the sentence. Below is a pretty typical example of how this works:
Fluffy, Sheri’s pug, slurped up the key lime pie the second it hit the floor.
“Fluffy” is the noun (a proper noun in this case since it is the name of the dog), and “Sheri’s pug” is the appositive phrase that defines the noun. “Sheri’s pug” is also a parenthetical element because it’s not necessary information, especially if you know Sheri and her dog. Even if you didn’t know, you could infer from the context of the sentence that Fluffy is a dog.
Fluffy slurped up the key lime pie the second it hit the floor.
However, were you to reverse the order of the noun and the appositive phrase, you could eliminate the parenthetical commas because the two ideas are so close. For example:
Sheri’s pug Fluffy slurped up the key lime pie the second it hit the floor.
Enclosing the name “Fluffy” in commas would be cumbersome in this case and not necessary even though it’s a nonessential element in the sentence. “Her dog slurped…” would still work just fine.
Interjections
Interjections are words that express emotion or command attention. They also appear in the middle of a sentence and need to be set off by commas. Examples of interjections are words/phrases like "oh!", “of course”, “indeed”, “however”, “to say the least.” For example:
Sheri’s dog, of course, slurped up the spilled pie the second it fell.
He did, however, ignore his full bowl of dog food.
He is, to say the least, a picky eater.
You get the idea. Note that if you begin the sentence with any of these sentences, the rules for comma placement change.
Absolute phrases
Absolute phrases consist of a noun or pronoun plus a participle and any modifiers. An absolute phrase can come at the beginning of the sentence or appear in the middle. It modifies the rest of the sentence but can be omitted comfortably without messing up the grammatical integrity of the sentence. It is additional information, but it is not necessary information.
Fluffy, having slurped up the pie, promptly puked on the new carpet.
Vocatives
When you address a person or animal by name in a sentence, that is a vocative. For example:
I swear, Fluffy, this is the last time I feed you pie!
The sentence is being addressed to the dog Fluffy. By using parenthetical commas to set off the name you can be sure it’s clear who you are speaking to. In this example, if you forgot the commas, it would still be pretty obvious that you were talking to the dog (or to someone); however, in this example, the commas are crucial to the meaning.
I know, Sheri!
versus
I know Sheri!
In the first example, the speaker is talking to Sheri. In the second, the speaker is talking about Sheri. There is a big different between the two, so you must include commas around vocatives to ensure clarity.
Something to note, however, is that when a parenthetical element follows a coordinating conjunction (for, and, nor, but, or, yet, so) we do not put a comma in front of the parenthetical element in order to avoid too many commas.
Sheri’s pug likes pie, but of course, he also enjoys raw steak.
USE A COMMA AFTER AN INTRODUCTORY DEPENDENT CLAUSE
The Chicago Manual of Style, 15th Edition, says “a dependent clause that precedes a main clause should be followed by a comma.” As you know, a dependent clause cannot stand on its own as a complete sentence. There are several types of introductory elements, so here are a few examples you might recognize:
Verbal Phrases
Verbals are verbs used as adjectives, adverbs, or nouns. Verbals may be based on verbs, but in the sentence, a verbal does not function as a verb.
Puking up pie, Fluffy realized he was hungry again.
Concerned, Sheri called the vet.
Both “puking” and “concerned” are based on verbs, but in these examples, neither one functions as a verb.
Subordinate Clause
Subordinate clauses contain a subject and a verb but cannot stand on their own because they contain words/phrases like “because”, “even though”, “when”, etc. that signify the clause needs more information to be complete. Subordinate clauses depend on the main clause to make sense. Examples:
Even though Sheri feeds him regular dog food every day, Fluffy will eat anything that spills on the floor.
Because Fluffy’s appetite is so insatiable, Sheri keeps dog treats all over the house.
When Fluffy gets too hungry, no unattended plate is safe.
Prepositional Phrases
Prepositional phrases are phrases that consist of a preposition such as “with”, “in”, “as”, “for”, etc. followed by a noun and connected with any necessary modifiers. “For a time” and “in the yard” are both prepositional phrases. Here’s a few examples of how to use them in an introductory element:
In a perfect world, Sheri wouldn’t have to put away every scrap of food whenever she left the kitchen.
Without Fluffy, Sheri would feel lonely.
Transitional Expression
A transitional expression shows relationship between a preceding sentence and the current sentence. Transitions such as “ for example”, “however,” and “of course” smooth the movement from one idea to the next in a series of sentences. They also must be followed by a comma.
Of course, Fluffy would also be lonely without Sheri.
All in all, Fluffy and Sheri were meant for each other.
Note: This rule is pretty straightforward, and a comma after an introductory element is NEVER wrong. However, there are times when you may omit the comma if leaving it out does not create confusion. For example:
When Fluffy eats pie he pukes.
I personally would use a comma after the word “pie” to add emphasis to the main clause “he pukes,” but it would be okay in this case to leave it out because it's very clear who is doing the puking and why.
YOUR MISSION
If you read my columns, then you are probably starting to grasp that I think proper grammar is important. However, I subscribe to the view that in order to break the rules, you must know them first. Your mission is to look up these rules yourself. Crack open a style guide, consult your favorite English teacher, or look it up online (at a reputable site). There are lots of great grammar resources online--Grammar Girl is my favorite. As a writer, it is your duty to be a master of your tools, and knowing how to properly use a comma is just one of the many tools in your mental toolbox that you need to perfect. Post your findings below. Grammar rules are not hard and fast and different sources many present different angles, but by looking them up, you will realize there is an underlying reason to each rule.
Happy looking!
About the author
Taylor Houston is a genuine Word Nerd living in Portland, OR where she works as a technical writer for an engineering firm and volunteers on the planning committee for Wordstock, a local organization dedicated to writing education.
She holds a degree in Creative Writing and Spanish from Hamilton College in Clinton, NY. In the English graduate program at Penn State, she taught college composition courses and hosted a poetry club for a group of high school writers.
While living in Seattle, Taylor started and taught a free writing class called Writer’s Cramp (see the website). She has also taught middle school Language Arts & Spanish, tutored college students, and mentored at several Seattle writing establishments such as Richard Hugo House. She’s presented on panels at Associated Writing Programs Conference and the Pennsylvania College English Conference and led writing groups in New York, Pennsylvania, and Colorado for writers of all ages & abilities. She loves to read, write, teach & debate the Oxford Comma with anyone who will stand still long enough.
