How and When to Use Periods, Commas, and Semicolons

Photo by Mark Duffel on Unsplash

Congratulations! You’ve finished your book!

Well, the first draft at least. Or maybe you’ve gone through and made some big-picture changes… Got rid of a couple plot holes, gave one of your protagonist’s allies a character arc… But as you’re reading through the first couple pages again, like most authors, you realize your book has a long way to go before it’s actually finished.

Fixing your periods, commas, and semicolons is part of this finishing up process. And while something as small as a comma is easy to overlook, if you don’t use it correctly, your book won’t be taken seriously.

But before you read any further, if you have not polished up your novel’s character development, worldbuilding, plot, or anything else that requires massive amounts of rewriting and reworking, DO NOT PROCEED. Otherwise, chances are you’ll spend hours and hours reading and re-reading your 100,000+ word behemoth, incorporating minor grammatical changes, only to realize that you need to completely re-write a subplot, and now all of the work you did to polish any sections that have anything to do with the subplot has gone to waste. So go take care of any big-picture changes you need to make.

Okay, did you finish fixing your plot holes? Good. Now allow me to bestow the knowledge of periods, commas, and semicolons on you.


Periods are arguably the easiest of the aforementioned punctuation marks to master. You put them at the end of complete sentences. Basically, if the phrase you just wrote makes sense all by itself, put a period at the end of it.

“You wrote a book” makes sense as a stand-alone phrase, so it’s a complete sentence, so it gets a period.

“When you write your book” does not make sense alone. When you finish your book… what? What happens then? Don’t put a period after it until you’ve made the phrase make sense alone. “When you write your book, you’ll realize you have to edit it.”


Commas are a bit trickier. There are more rules for them than there are for periods, and then there are exceptions to the rules, so buckle up.

Rule 1. Use commas before “and” to combine independent clauses.

An independent clause is simply a phrase that could be a stand-alone sentence. In the sentence “I ran outside, and I saw a moose” both “I ran outside” and “I saw a moose” could be complete sentences alone. So, you use a comma.

The same rule applies to combining independent clauses with conjunctions besides “and.”

“She grew up in the country, but he was raised in the city.”

However, don’t use commas to combine a dependent clause to an independent clause if the independent clause comes first. A dependent clause is a phrase that cannot be a complete sentence by itself; it’s dependent on another clause. The sentence “I ran outside and saw a moose” does not get a comma between “I ran outside” and “saw a moose” because “saw a moose” makes no sense alone. If you wanted to use a comma between the two clauses, you’d need to make “saw a moose” an independent clause by changing it to “I saw a moose.”

Rule 2. Use commas after dependent clauses that start a sentence.

Remember how I just said not to use a comma when combining an independent clause with a dependent one? Well, when the dependent clause comes first, then you use a comma between it and the independent clause. I told you commas were tricky.

“When I ran outside, I saw a moose.”

Rule 3. Use a comma after an introductory phrase.

“Running out of the house, I saw a moose.”

Rule 4. Use a comma after an adverbial phrase (if you want to).

“Across the rope bridge, there are elephants.”

Basically, adverbial phrases tell you the Where, Why, When, and How of the sentence. So if your sentence starts off with a phrase that is giving information on any of those “three Ws” or the How, then you can follow the phrase with a comma.

“Under the sea (where), there are sharks.”

“Mistakenly thinking that a degree would get me a job (why), I went to college.”

“The day after tomorrow (when), I’m going to stop procrastinating.”

“Meticulously (how), she edited her novel.”

You don’t always have to use this comma, however. It’s best to use it when the adverbial phrase has four or more words or when not using it would cause confusion. But “Outside the house there is a moose” is perfectly valid.

Rule 5. Use commas to separate items in lists.

In the sentence “She wants to go to England, France, and Italy” you’re supposed to use commas between each item in the list. However, the last comma, the comma before “and Italy” is optional. Whether or not you use a comma before the last list item is up to your stylistic preferences and what your publishing house wants.

Rule 6. Use commas between adjacent adjectives that modify the same word.

In the sentence “The insane, angry elephant attacked” you put a comma between “insane” and “angry” because they’re both modifying the word “elephant.” An easy way to remember this is if you can insert the word “and” between your adjectives, then you need a comma between them. “The insane and angry elephant attacked” makes perfect sense, thus, without the “and,” the adjectives need a comma between them.

However, if the first adjective is modifying the second adjective, then you do not put a comma between them.

Example: “She had bright blue eyes.” If you put a comma between “bright” and “blue,” then the sentence would cease meaning that her eyes were a bright shade of blue and would instead mean that her eyes were both bright and blue. That’s the power of commas.

Rule 7. Use commas when your character is addressing someone.

“Bill, what are you doing?” he asked. Or: “What are you doing, Bill?” Always put a comma before or after a name when that person is being spoken to.

Rule 8. Use commas around phrases that interrupt your sentence.

“I was singing, if you can call it that, and strained my vocal cords.”

The phrase “if you can call it that” isn’t necessary and interrupts “I was singing and strained my vocal cords.” Basically, if you can take a phrase out of the middle of a sentence and the sentence still makes sense, put commas around the phrase.

Another example: “My sister, who is tall, likes football.”


Semicolons have fewer rules than commas and may be a bit simpler.

Rule 1. Use semicolons to join two independent clauses that are closely related.

“I like pineapple on pizza; others consider pineapple on pizza sacrilegious.”

“I love cereal; however, I hate when it gets soggy.”

If you could make each phrase its own sentence, but they’re related enough that you could combine them with an “and” or “but,” but you don’t want to use an “and” or “but,” then the semicolon is for you.

Rule 2. Use semicolons to separate items in a series when those items have commas in them.

“To write a novel you need imagination; a computer, or a pen and paper if you prefer; and perseverance.”

Now that you have a few more grammar tools under your belt, editing your book should be a bit easier. So grab a cup of coffee (or tea), pull up a chair, and start editing away!


Sophia Uhlenhoff

Sophia is a writer of soft sci-fi and fantasy, who spends more time daydreaming about her books than actually writing them. She also enjoys procrastinating by playing Skyrim. If you see her, tell her to go write.

Currently, she's a student of creative writing at Boise State University and a Chaos Gate author at Fiction Vortex. Her dream is to live in a tree house next to a waterfall and have a pet bunny named Mr. Floofers.

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