What is a comma?

A comma is a type of punctuation mark used to signify a separation or slight pause in a sentence. There are many places where a comma is necessary, and as importantly, there are several places where a comma should NEVER be used. In this blog, I’m going to outline four places where you should always use a comma AND give you a bonus three times you should never use a comma. Complete with examples, this blog post will be a handy resource the next time you find yourself stuck on whether or not you should use a comma.

So, keep reading to find out four times you should ALWAYS use a comma and three times you should NEVER use a comma.

4 Times You Should Use a Comma

1. You should always use a comma between two independent clauses (as long as you also use a coordinating conjunction).

An independent clause is a clause that contains a subject and a predicate but does not contain a subordinating conjunction. (Think: a simple sentence). When you combine two independent clauses with a comma and a coordinating conjunction, you have a compound sentence (and a correct usage of a comma)! 

Now, you may be wondering what a coordinating conjunction is. There are 7 coordinating conjunctions in the English language, and you can remember them using the acronym FANBOYS.

F – for

A – and

N – nor

B – but

O – or

Y – yet

S – so

If you have two independent clauses + a comma + a FANBOYS, you have a compound sentence!

Example Time

Bob went to the store. ? one independent clause = simple sentence

He bought some apples. ? one independent clause = simple sentence

Bob went to the store, and he bought some apples. ? two independent clauses + comma + FANBOYS = compound sentence 

2. You should always use a comma after an introductory dependent clause.

A dependent clause is a clause that contains a subject, a predicate, AND a subordinating conjunction. On its own, a dependent clause is not a complete sentence, but when it’s combined with an independent clause, it becomes a complex sentence. When your complex sentence begins with a dependent clause, you should always use a comma after the dependent clause.

Now, you may be wondering what a subordinating conjunction is. There are many subordinating conjunctions in the English language, but some common examples include: after, although, as, when, while, until, because, before, if, since.

If you have a dependent clause + a comma + an independent clause, you have a complex sentence (and the correct usage of a comma)!

Example Time

After running around the block five times ? one dependent clause = not a sentence

Mary was tired. ? one independent clause = simple sentence

After running around the block five times, Mary was tired. ? one dependent clause + comma + one independent clause = complex sentence

3. You should always use a comma between all items of three or more in a series.

There are several different types of series: series of words, series of phrases, and series of clauses. No matter what type of series you have in your sentence, you should use commas between all items of three or more. 

The last comma in the series is called the Oxford comma, and it’s technically optional (but I’m a big fan of the Oxford comma and will probably judge you if you don’t use it). 

Example Time

Karen bought oranges, apples, and pears. ? series of words

He looked through his backpack, under his desk, and in his pencil case. ? series of phrases

She said that she would be on time, that she would pay attention, and that she would ask questions. ? series of clauses

4. You should always use a comma around non-restrictive clauses, phrases, and words.

Non-restrictive clauses, phrases, and words are clauses, phrases, and words that can be removed from the sentence without changing the meaning of the sentence.

Not sure if a clause, phrase, or word is non-restrictive? Try removing it from the sentence. If the sentence still makes sense, the clause, phrase, or word is non-restrictive.

Example Time

My boss John is a nice man. ? My boss is a nice man. ? My boss, John, is a nice man.

In this sentence, “John” is non-restrictive and should have commas around it.

Jenna who spent the last three days hiking is back at work. ? Jenna is back at work. ? Jenna, who spent the last three days hiking, is back at work.

In this sentence, “who spent the last three days hiking” is non-restrictive and should have commas around it.

3 Times You Should NEVER Use a Comma

1. You should never use a comma between two independent clauses when a coordinating conjunction is not present.

We now know what an independent clause is, and we know the correct way to use a comma to form a compound sentence. Now, let’s talk about the incorrect way to form a compound sentence. You should never use a comma to join two independent clauses without a FANBOYS. 

If you want to combine two independent clauses without a FANBOYS, you can use a semicolon, but you should never use a comma without a FANBOYS. Doing this creates a comma splice, and it is the cardinal sin of grammar.

Example Time

Bob went to the store, he bought some apples ? comma splice = wrong

Bob went to the store; he bought some apples ? semicolon = correct

2. You should never use a comma after an independent clause when a dependent clause follows.

We also now know what a dependent clause is, and that if you start a complex sentence with a dependent clause, you need to use a comma. However, you do NOT need a comma if your complex sentence ends with the dependent clause.

I see this mistake a lot. I think it stems from the fact that a lot of people naturally pause between the independent and dependent clauses when they speak, so they think they need to put a comma in their writing. Regardless, you should never use a comma after an independent clause when a dependent clause follows.

Example Time

Mary was tired, after walking around the block five times. ? comma after independent clause = incorrect

Mary was tired after walking around the block five times. ? no comma after independent clause = correct

3. You should never use a comma around restrictive clauses, phrases, and words. 

We now know that non-restrictive clauses, phrases, and words are clauses, phrases, and words that are non-essential to the sentence. Logic would follow, then, that restrictive clauses, phrases, and words, are clauses, phrases, and words that are essential to the sentence. 

Again, a good way to test whether or not a clause, phrase, or word is restrictive is to take it out of the sentence. If the sentence doesn’t make sense, the clause, phrase, or word is restrictive, and you shouldn’t use commas around it.

Example Time

We flew to Spain for our vacation. ? We flew for our vacation (to where?) ? We flew to Spain for our vacation.

In this sentence, “to Spain” is restrictive and should not have commas around it.

The man sitting in the back of the hall is the composer. ? The man sitting is the composer (where?) ? The man sitting in the back of the hall is the composer.

In this sentence, “in the back of the hall” is restrictive and should not have commas around it.

That’s all for now folks!

Until next post, may your commas be correct, and your grammar be groovy!