When To Use a Comma

Are you ever writing a sentence and realize that you aren’t sure why you have to write it a specific way? Maybe, you’re proofreading your paper and come across a punctuation mark, and you’re not sure if, or why, that’s what goes there.

General Comma Functions

A comma is a punctuation mark used to separate words, ideas, and phrases. A punctuation mark is a symbol or sign used to direct the reader’s understanding of a sentence. For example, we use periods to mark the end of a sentence, exclamation points to show excitement, and question marks to show that the sentence should be read as a question.

Commas function as a sort of pause between parts of a sentence rather than as an end or as a question. Commas are usually placed in the sentence where you would most naturally take a breath if you were reading the sentence aloud. We also use commas to add emphasis to our writing, to make the reader pause and think about what is being read, and to allow for more information to be said in the clearest way possible. Today, we’ll look at how and why you should use commas.

Direct Address

In writing and speech, we use commas when giving a direct address to someone. A direct address is simply when you are directing your sentence to a specific person. For this reason, a comma must come either immediately before or after the address is made. Placement of the comma will just depend on when the address is made in the sentence. Let’s look at a couple of examples:

Example 1

Mom, are you picking me up from school?

In this example, you would place your comma after the word Mom to add clarity to the sentence and to specify that it is Mom you are speaking to.

Example 2

If we change the structure of the sentence, it might look something like this:

Are you picking me up from school, Mom?

In this one, the comma comes directly before Mom. By placing the comma before Mom, you are showing that the question is directed toward Mom rather than someone else. Here’s a third way you could use commas for a direct address in your sentence:

Example 3

Hey, Mom, are you picking me up from school?

In each of these examples, a comma is used to show that the question is directed to Mom. If you didn’t use your comma(s), it would be confusing as to whom your sentence was directed. This is an example of using commas for clarity in your writing.


You should also use a comma when writing dates. When writing the month, day, and year in the middle of a sentence, you will use commas to separate each piece of information. For example:

Example 1

Today, Friday, September 14, 2018, is the day Mom will pick me up from school.

You need to use a comma when writing your date because without one, your sentence becomes too congested with numbers and words, and it becomes more difficult to read. Using commas when writing the date also allows for interrupting information to be seamlessly included in the middle of a sentence without disrupting its flow.

Example 2

As I’m sure you’re learning, the English language has many exceptions to its rules, such as this next one. If you are writing the date with just the month and the year, do NOT use a comma to separate the month and year. Additionally, you will NOT use a comma after the year.

My birthday will happen in September 2018.

In this example, it would disrupt the flow of the sentence to include a comma and force a pause where one is not necessary.


When writing locations, a comma should be used to separate cities from states and to separate cities from countries. A comma is used at this time to show that the city is part of something larger, a state or country. Additionally, commas are used to separate counties and states as well as countries and continents. Let’s look at some examples:

Example 1

Mary is from Houston, Texas.

In this example, we used a comma to separate a city from a state.

Example 2

She has been to Paris, France, but she has not been to Paris, Texas, United States of America.

In this example, we use a comma to separate a city from a country and to separate a city, state, and country.

Example 3

She lives in Harris County, Texas.

Here, a comma is used to separate a county and a state.

Example 4

Mary has a friend from Ghana, Africa.

Lastly, we use a comma to separate a country from a continent.

Separating List Items

Another time you’ll want to use a comma is when you’re writing and using a listing method to describe certain objects or situations. When this happens, you’ll want to use commas to separate items in your list. By separating items in a list with a comma, your sentence(s) can be read clearly, and you won’t become tongue-tied when reading. Here’s an example:

While at the grocery store Mom bought apples bananas beans bread water and ice cream.

In this example, commas are nonexistent. When you begin to write your sentence and you want to include a list, be sure to go in and add your commas. Let’s see what that looks like:

While at the grocery store, Mom bought apples, bananas, beans, bread, water, and ice cream.

Wow, that looks so much better, don’t you think? By using commas in your lists, each item is perfectly distinguished from the next. Each time you write a list of three or more things, you’ll want to include your commas so as to maintain the flow of the sentence.

Connecting Independent Clauses

You’ll want to use a comma when adding a conjunction (and, if, or, but, yet, etc.) to combine two independent clauses. An independent clause is a sentence that can stand alone, meaning the sentence contains at least one subject and verb in agreement. In the case that you are wanting to combine two complete sentences, use a comma and a conjunction to get the job done! Here’s an example sentence:

Mom went to the grocery store. She bought apples and bananas.

Here are two independent clauses, both containing subjects and verbs. Combining these sentences with a comma and conjunction relieves you of having to keep writing short, little descriptive sentences. By combining the two, you are adding variety to your writing. Writing with a variety of sentence styles is a great way to keep your reader interested and keep your work interesting!

Let’s try rewriting those sentences with a comma and a conjunction instead:

Mom went to the grocery store, and she bought apples and bananas.

That looks so much better! We were able to combine two independent clauses, both having subjects and verbs, just by adding a comma and a conjunction. Now our sentences will read smoothly rather than being choppy like they were before.

Separating Certain Adjectives

Lastly, a comma should be used between two adjectives of the same weight, describing the same noun. This just means that if you’re using two adjectives that roughly convey similar meanings, belong to the same category of description, and can be swapped in the sentence without changing the meaning, you should use a comma. Let’s work through some examples, together.

Example 1

Mom only buys ripe, grown fruit at the grocery store.

In this example, ripe and grown are saying similar things about the fruit that Mom buys. One way to test whether or not the adjectives need a comma is to place the word and between them and switch their placements.

Mom only buys ripe and grown fruit at the grocery store.

Mom only buys grown and ripe fruit at the grocery store.

The meaning of the sentence does not change no matter which way you write it. For this reason, you should place a comma between ripe and grown. If the adjectives do not describe the noun in the same weight, then a comma is not necessary.

Example 2

Mom picked up a bag of large old bread by accident.

Here, you would NOT need a comma between large and old. The two adjectives, size and age describe different qualities of the bread that was bought. Because they are different descriptors, a comma would not be used.

Remember, we use commas to add a pause to our sentences in order to make them clearer for the reader. When we have a lot of information to include in our writing, it’s important to make it as easy as possible to keep up with. These are just a few instances in which you should be using a comma, and with enough practice, you’ll get the hang of them!



by Mometrix Test Preparation | Last Updated: October 6, 2021