Comma rules

In a nutshell

​A comma is a punctuation mark that helps you make sentences less cluttered and easier to read. They do a number of jobs to make this happen. Commas can be used to separate items in a list, to separate coordinate adjectives, to separate clauses and lastly to punctuate direct speech. 

Commas and lists

​Commas can be used when you want to separate items in a list. You can do this by simply using a comma after each item.

Example

My bag contained shoes, a jacket, a hat and sunglasses.

Commas and adjectives

​You can also use commas to separate coordinate adjectives. Coordinate adjectives are two or more adjectives of equal rank that modify the same noun. As a result of this, the order of the adjectives is not that important. 

Example

The dangerous, preoccupied driver weaved through the city streets looking at his phone.

​This can also be written as:

​The preoccupied, dangerous driver weaved through the city streets looking at his phone.

Note: There is sometimes an order in which to write adjectives – particularly when multiple (three or more) adjectives are used before a noun – but don't worry about that now. Additionally, make sure not to place a comma after the last adjective in the sentence.

Commas and clauses

Subordinate clause

​Before going into how commas are used to separate clauses, it's important to understand what a subordinate clause is. A subordinate clause is a clause that cannot stand alone as a complete sentence, it only adds additional information to the main clause. 

In the example below, the subordinate clause is highlighted blue (note how the clause cannot be a sentence by itself).

Example

Before I start the movie, I like to eat the popcorn.

I like to eat the popcorn before I start the movie.

In most cases, when the subordinate clause is at the beginning of a sentence, a comma is placed after it. When the subordinate clause is at the end of a sentence, then there is no comma.

Main clauses and coordinating conjunctions

​When a main clause is joined by a coordinating conjunction (for, and, nor, but, or, yet, so), you will also need to place a comma before the conjunction.

Example

I went to the zoo, and Sam went to the chocolate factory.

Commas and direct speech

Direct speech

​In case you forgot, direct speech is a report of the exact words used by a speaker or writer. These words are placed in between quotation marks ("...").

A comma is placed before introducing the speech.

Example

The woman said, "What a cute dog."

Take note, if the sentence carries on after the speech, another comma should be used before the last set of quotation marks (unless the speech ends with a question mark or exclamation mark, in which case no comma is used).

Examples

​The woman said, "What a cute dog," and continued to pet it.

The boy interjected, "Yay!" and opened his presents.

Comma splicing

A comma splice happens when you use a comma to connect two main clauses when, in fact, a full stop is needed. This is something you should avoid in your writing. A comma is simply not enough to show the relationship between two main clauses.

Example

The house was on fire, I was horrified.

Which should actually be:

The house was on fire. I was horrified.

Alternatively, there are two ways you can fix this besides using a full stop:

Using a conjunction

You could add a conjunction immediately after the comma to connect the two clauses.

Example

The house was on fire, and I was horrified.

Using a semi-colon

You could also change the comma to a semi-colon instead. Semi-colons are another good way to join two (related) main clauses together.

Example

The house was on fire; I was horrified.