Determining when to insert a comma before a phrase or clause that begins with because requires thoughtful analysis. In this post, I’ll walk you through two kinds of examples: sentences with positive verbs and sentences with negative verbs. The explanations and examples are derived from Claire Cook’s Line by Line (115–16).
Sentences with Positive Verbs
When the main clause of a sentence contains a positive verb, inserting a comma before because makes what follows nonessential to the meaning of the sentence:
Alex ordered the book online. Robert also ordered the book online, because he was running out of reading material.
In the sentence above, because he was running out of reading material is not essential to the meaning of the sentence. The point is that Robert, like Alex, ordered the book online. The reason Robert ordered the book online is simply additional information. But if the reason is necessary to convey the writer’s meaning, then the comma should be omitted:
Alex ordered the book online because she was too tired to go to the bookstore. Robert ordered the book online because he was running out of reading material.
In this case, the writer wishes to emphasize the reason each person ordered the book online.
Sentences with Negative Verbs
When the main clause of a sentence contains a negative verb, the insertion of a comma before because lets the reader know “the reason for a negative statement” (Cook 116):
I didn’t order the book online, because I was running out of reading material. I decided to buy the book from the shop down the street instead.
In the first sentence above, the reason the writer didn’t order the book online is because the writer was running out of reading material. As the second sentence indicates, the writer decided it would be quicker to get the book from a shop.
The omission of a comma indicates that what follows because “gives an incorrect explanation” (Cook 116):
I didn’t order the book online because I was running out of reading material.
Here, running out of reading material is not the reason the writer ordered the book online, as the second sentence below makes clear:
I didn’t order the book online because I was running out of reading material. I ordered it online to support Bookshop, a new online store.
But without that second sentence, the meaning of the first sentence is ambiguous. Did the writer order the book online because the writer was running out of reading material? Or did the writer order the book online for some other reason? Thus, as always when a sentence is unclear, it’s best to revise. In this case, you might rewrite the sentence as follows:
It was not a shortage of reading material that led me to order the book online. I ordered it online to support Bookshop, a new online store.
Work Cited
Cook, Claire Kehrwald. Line by Line: How to Edit Your Own Writing. Houghton Mifflin Harcourt, 1985.
8 Comments
Carolyn Poole 17 November 2020 AT 03:11 AM
Thank you! You cleared up something that always bothered me when correcting student essays. To be honest, I didn’t think one ever used a comma before because.
Bartleby 17 November 2020 AT 12:11 PM
You wrote: The omission of a comma indicates that what follows because “gives an incorrect explanation” (Cook 116):
I didn’t order the book online because I was running out of reading material.
Here, running out of reading material is not the reason the writer refrained from ordering the book online . . . .
I believe you meant to say "Here, running out of reading material is not the reason the writer DID order the book online, not REFRAINED from ordering it.
Jennifer A. Rappaport 18 November 2020 AT 01:11 PM
Thanks! I have made the correction. Another good reason to avoid this sentence structure in the first place: it's confusing to read and confusing to explain!
Deb Layton 18 November 2020 AT 04:11 PM
I'm not sure that I'm following this. "Because" acts as a subordinating conjunction that begins an adverb clause, so I don't see how you need a comma before the word in your examples. If the sentence starts with an adverbial clause, then you use a comma after it as follows:
Because Robert was running out of reading material, he ordered the book online. I'm not aware of a rule for using the comma if you flip the order there. Perhaps I'm just a traditional grammarian, and this is a "new rule" like using "because" as a preposition has become standardized. Can you clarify?
Jennifer A. Rappaport 19 November 2020 AT 08:11 AM
Thanks for your comment. As noted above, the explanations and examples are derived from Claire Cook's Line by Line. Claire Cook worked at the MLA for many years, and her book was published in 1985, so the guidance on commas with because has been around for some time.
Kerry Sauer 11 January 2022 AT 01:01 AM
Hi Deb, I had the same question. I may try to take a looking at Cook's book to see where she derived the rule. Is this an observation or is based on another source?
Habib 23 February 2021 AT 03:02 AM
When we start with a subordinate conjunction, do we put comma between the clauses or not?
C. Barney Latimer 09 March 2021 AT 10:03 AM
Yes, when a sentence begins with an adverbial clause introduced by a subordinating conjunction like because, the adverbial clause is always followed by a comma. For instance, if the example in this post began with because, it would read, “Because I was running out of reading material, I didn’t order the book online.”
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