Rule 1: When “since” is a coordinating conjunction that means the same as “because,” use a comma if the first clause contains a negative verb and the second clause is independent.
- Correct: She couldn’t attend the conference, since she was sick last week.
- Incorrect: She couldn’t attend the conference since she was sick last week.
However, do not use a comma in all other instances when you use “since” to mean “because.”
- Correct: She is in great condition since she exercises every day.
- Incorrect: She is in great condition, since she exercises every day.
Rule 2: Do not put a comma before “since” when it is a preposition or conjunction that talks about time.
- Correct: I have not had a vacation since last Christmas.
- Incorrect: I have not had a vacation, since last Christmas.
Would you like to learn more regarding how to use commas with the word “since”? In the rest of the article, we’ve explained the rules in more detail and provided additional example sentences.
When to Use a Comma Before “Since”
The occasions when you need a comma before “since” are listed in Rule 1.
Rule 1: Use a comma before “since” when the first clause has a negative verb and the word since means “because.”
In these examples, the clause that contains “since” is independent and often provides the “reason” for something happening or not happening.
- He didn’t come to the party, since he knew I would be there.
- We weren’t in the house when you called, since we went on a family trip.
However, you shouldn’t put a comma before “since” when it means “because” if there is no negative verb or the clauses are dependent.
- He didn’t go to bed since he had too much homework.
- They wanted to get married since they loved each other.
When to Avoid a Comma Before “Since”
You can refer to Rule 2 to understand when you shouldn’t use a comma before “since.”
Rule 2: You shouldn’t use a comma before “since” when it refers to time.
When referring to time, the word “since” is either a preposition or a conjunction, and you should not use a comma.
In this form, “since” usually appears in the middle of a sentence, but it can also appear at the end of a sentence.
- We have been here since 8 pm, and you still haven’t taken our order.
- We have been together since September 2020.
- He has earnt more money since he switched jobs.
- I lent him $20, and I haven’t seen him since.
Conclusion
You must use a comma before “since” when it means “because,” and the first clause is negative. E.g., “I didn’t buy the car, since I must pay for my wedding.” Furthermore, do not use a comma when “since” refers to time. E.g., “I have lived here since 2019.”