How To Use Commas | Return to Film Library
Commas can be used to separate items in a list or series. For example: “I like studying physics, teaching grammar, and reading.”
We use commas to make our writing clearer. Take this sentence as an example: “The park was filled with chirping birds, barking dogs and children.” Without a comma after dogs, it sounds like the children were barking too. Adding a comma makes this sentence clearer and less frightening. “The park was filled with chirping birds, barking dogs, and children.” Today, we’ll look at the three most important comma rules.
Rule Number One. Put a comma before a coordinating conjunction that separates two independent clauses.
The words for, and, nor, but, or, yet, so are all coordinating conjunctions.
You must use a comma to separate independent clauses in a compound sentence when they are separated by one of these coordinating conjunctions. Make sure to place the comma after the first clause and before the coordinating conjunction that separates the clauses.
Let’s see this in action.
Our sentence is
“The alien has a spaceship, but he doesn’t have any friends.”
Alien: Hello! I have a spaceship but no friends to play with me.
Einstein: Let’s first check and see if this sentence contains independent clauses. An independent clause can stand on its own as a complete sentence.
“The alien has a spaceship” is a complete sentence with a subject and a verb. So is “He doesn’t have any friends.”
“But” is a coordinating conjunction. Thus, we need to place a comma before the but in this sentence.
Here is the corrected sentence:
“The alien has a spaceship, but he doesn’t have any friends.”
Remember to only use a comma when you have a coordinating conjunction separating two independent clauses.
You can’t write:
“The alien has a spaceship, he doesn’t have any friends”
That is an error called a comma splice.
Rule Number Two. Use a comma after introductory words, phrases, or clauses in a sentence.
Yes, my spaceship really flies.
Alien, where do you want to go in your spaceship?
Alien: I’m going to travel to a distant planet to find a friend.
Einstein: Introductory adverbs are usually set off by a comma also unless they are followed directly by the word they are modifying.
For example: Quickly, the alien flew away in his spaceship.
Quickly is modifying how the alien flew away in his spaceship, but not the alien himself. Since it is not directly before “flew” you need to use a comma. But you do not need a comma in this sentence.
Quickly fly away!
In this sentence, quickly is modifying how the alien flies.
Rule number two tells us that we also need to use a comma after introductory phrases. You need to use a comma to separate a group of prepositional phrases of more than four words when the phrases are placed at the beginning of your sentence.
You do not need to use a comma in this sentence because the prepositional phrase is less than five words. It is short and clear.
On a strange planet the alien landed his spaceship.
But the sentence would probably be easier to read if you wrote it this way:
The alien landed his spaceship on a strange planet.
You would need to use a comma if your prepositional phrase was longer than four words. For example:
Deep inside a strange planet, the alien landed his spaceship.
You also need to use a comma to separate introductory participial phrases (words that end in -ing) and infinitive phrases (like “to run” or “to fly”) that are used as modifiers.
Flying faster than lightning, the alien reached a strange planet.
To reach the planet before dinner, the alien must fly faster than lightning.
Alien: Wow, I have landed on a strange planet.
Einstein: Rule Number Two tells that we also need commas after introductory clauses.
An adverb clause begins with a subordinating conjunction and may tell us what time the sentence takes place or in what place or to what extent.
While he was on the planet, the alien made a new friend.
However, it is important to remember that if a sentence ends with an adverb clause, you do not use a comma.
The alien made a new friend while he was on the planet.
Alien: Would you like to be friends?
Alien’s friend: Yes!
Rule Number 3. Use commas to set off elements that interrupt or add information in a sentence.
Conjunctive adverbs are adverbs which join different parts of a sentence. Several examples of conjunctive adverbs are “therefore, indeed, instead, however.”
Here’s how you punctuate a sentence that use a conjunctive adverb to interrupt the sentence:
However, he needs to leave soon to get home for dinner.
You place commas on either side of your conjunctive adverb if you use it in the middle of your sentence.
He needs to leave soon, however, to get home for dinner.
Rule Number 3 also tells us that we need to use commas if we add a modifying word, phrase, or clause to our sentence that presents information which is not essential to identify the noun or the meaning of the sentence.
That sounds a bit complicated but it will make sense once we see it in action.
Anyone who builds a spaceship is a genius.
We don’t need commas around “who builds a spaceship” because that phrase is necessary in order to identify the noun. If we remove it, we will get a very different sentence. Anyone is a genius. And that’s not what we originally meant.
However, we do need commas in this sentence:
The alien, who has now found a new friend, is very happy.
We know that this sentence is about the alien. The clause who found a new friend adds information, but it is not necessary to identify the noun it modifies. Drop the clause and we still know who is happy: the alien.
Alien: I am so happy to have made a new friend.
Einstein: Let’s recap those three comma rules.
Rule Number One. Use a comma before a coordinating conjunction that separates two independent clauses. Rule Number Two. Use a comma after introductory words, phrase, or clauses in a sentence. Rule Number Three. Use commas to set off elements that interrupt or add information in a sentence.
If you know how to use commas in all of these instances, you will be a comma expert.
Alien: Thank you, Mr. Einstein.
Einstein: Thanks for watching! Bye for now.