Do We Put a Comma Before "When"?

Rule 1: You should always put a comma before “when” if it starts a non-essential clause in a sentence.

Correct: In 1981, when he was born, there was no internet, and people still used landline telephones.
Incorrect: In 1981 when he was born, there was no internet, and people still used landline telephones.

Rule 2: Do not use a comma if “when” separates independent and dependent clauses.

Correct: He felt very excited when he saw the results.
Incorrect: He felt very excited, when he saw the results.

So, the rules seem pretty simple. However, in the rest of the article, you can learn more about the different rules as well as the exceptions to these rules.

Also, we’ve gathered some great examples that show you exactly how to use commas with the word “when.”

After reading the next sections you should have no more doubts about the comma rules concerning the word “when.”

When to Use a Comma Before “When”

If you need to decide when to use a comma before “when,” you should refer to Rule 1.

Rule 1: Use a comma before “when” if it is the first word of a non-essential clause.

You will know if it is non-essential because if you remove it, the sentence still makes sense. That is, after all, what “non-essential” means.

Here are some example sentences showing you the concept:

That afternoon, when he was supposed to be at school, he went to the park.
In April, when we signed the contract, the rent was only $750, now it’s $1000.
In the 93rd minute, when the game was almost over, he equalized the score.
My sister, when she was living in New York, often visited Central Park.
Last summer, when the weather was particularly hot, we installed an air conditioner.
My grandmother, when she was younger, used to be a dancer.
The movie, when it finally started after several delays, was absolutely worth the wait.
This computer, when it was first released, was the most advanced on the market.
Our cat, when it feels playful, chases its tail around the room.

Notice how the above sentences still make sense if you remove the clause starting with “when.” The clause just adds to the sentences but it isn’t necessary for you to get the main point.

Now, let’s explain to you when you shouldn’t use a comma before “when.”

When to Avoid a Comma Before “When”

Rule 2 explains when you should avoid a comma before “when.”

Rule 2: You shouldn’t use a comma before “when” if it separates a dependent clause from an independent clause.

You will know if one of the clauses is dependent because it doesn’t make sense unless combined with the other clause. On these occasions, you should not use a comma.

Have a look at these examples:

He loses everything when he goes out with his friends.
I don’t like it when people are rude to me.
She becomes more focused when she listens to classical music.
The flowers bloom when spring arrives.
The kids get restless when they have too much sugar.
She feels happiest when she’s painting or drawing.
The team always performs well when they practice consistently.
My hair gets frizzy when the humidity is high.
He usually wakes up when the sun rises.

However, if “when” appears in the middle of a sentence and connects two independent clauses, you should use a semi-colon before it rather than a comma.

Here are some examples:

He decided he would go out; when, from the kitchen, his mother shouted that he was staying in
He tried to talk to the students; when, suddenly, the fire alarm sounded.
I wanted to start the meeting; when, unexpectedly, the power went out.
He was about to propose; when, out of nowhere, a flash mob started dancing.
She was reading her book quietly; when, to her surprise, her cat jumped onto her lap.
We were preparing for a calm evening; when, all of a sudden, guests arrived.
They were hiking up the hill; when, abruptly, it started to rain.
She was setting the dinner table; when, startlingly, the lights dimmed.
The children were playing outside; when, unexpectedly, a rainbow appeared in the sky.

Conclusion

You should use a comma before “when” if it starts a non-essential element. E.g., “In 2008, when he was born, the world was very different.” In contrast, if “when” separates a dependent and independent clause, don’t put a comma. E.g., “I love it when you say nice things to me.”