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Commas and Conjunctions
Should I use a comma before a conjunction?
Writers often ask whether they should put a comma before a conjunction (e.g., "and," "or," "but"). Use a comma before a conjunction that merges two sentences into one. Also, use a comma before the conjunction in a list of three or more items, but only if that's your local convention.(1) Use a comma before a conjunction if you're merging two "sentences" into one with a conjunction.
For example:
I like pies
+ , but
+ I hate sausage rolls.
- Sentence 1: I like pies.
- Sentence 2: I hate sausage rolls.
- The Two Sentences Merged: I like pies, but I hate sausage rolls.
With lists, if there are just two list items, don't use a comma before the conjunction. For example:
- I like burger and fries.
- I like burger, shake, and fries.
(
)
(The comma before "and" is called a "serial comma" or an Oxford Comma.)
- I like fish, chips and peas
(
)
(Be aware that lots of institutions in the UK use the Oxford Comma, i.e., they use the same convention as Americans.)
Infographic Explaining Commas before Conjunctions
This flow diagram explains when to use a comma before a conjunction:
More about Commas before Conjunctions
Unfortunately, there is no simple rule like:- Always use a comma before "and."
- Never use a comma before "and."
Use a Comma to Join Two Independent Clauses
When two standalone sentences (or independent clauses) are joined together using a conjunction (e.g., "and," "but," "or"), the conjunction should be preceded by a comma.We eventually found the cave
+ , but
+ Jack was not there.
- Sentence 1: We eventually found the cave.
- Sentence 2: Jack was not there.
- The Two Sentences Merged: We eventually found the cave, but Jack was not there.
Examples of a Comma before a Conjunction That Joins Two Independent Clauses
In these examples, the conjunctions are in bold:- Our team was given 2 minutes' notice, but theirs had been training for weeks.
- I have spoken to Sarah, and she has confirmed the delivery date.
- I have spoken to Sarah, and confirmed the delivery date.
- We built the hut in an hour and then painted it.
More about Commas and Sentence Structure
A sentence made up of two halves, either of which could be a standalone "sentence," is known as a compound sentence. The conjunction that joins the two halves of a compound sentence is preceded by a comma.Here are some other sentence types:
- I love milk. (This is a simple sentence.)
- I cannot drink it when it is warm. (This is a complex sentence. A complex sentence is made up of an independent clause ("I cannot drink it") and a dependent clause ("when it is warm").)
- I love milk, but I cannot drink it when it is warm. (This is a compound sentence. The comma before "but" is correct.)
Comma with Conjunctions in Lists
Don't Use a Comma to Join Two List Items
When there are two items in a list, there is no need to separate the list items with a comma. For example:- Fish and chips
- She would only eat ham and eggs.
- I have never been to London, or Paris.
With Three List Items, Use a Comma If You're an American (or an Advocate for the Oxford Comma)
When there are three or more list items, things start to get complicated. There are two conventions. Generally speaking, Americans will use a comma, but Brits won't. (There's more on this below.) For example:- Fish, chips, and peas
(
)
- Fish, chips and peas
(
)
- I have never been to London, New York, or Paris.
(
)
(
)
The Oxford Comma causes great debate among grammarians. The bottom line is this: Use the convention that your institution uses and then be consistent throughout your document. Read more about commas in lists. Read more about the Oxford Comma.
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