The short answer to that question is: it depends how you’re using and.
The difficulty is that there is no single rule that applies to all situations. However, there are a couple of general rules we follow.
1. We usually put a comma before and when it’s connecting two independent clauses. (An independent clause is one that can stand by itself as a simple sentence.)
2. We can put a comma before and in a list where we list three or more items.
Joining two independent clauses
When we use and to join two sentences that relate to each other – or independent clauses, it requires a comma before and.
Here are two independent clauses:
The dog chased the cat. The cat ran away.
Here’s how we join those independent clauses:
The dog chased the cat, and the cat ran away.
Make sure that the sentences you are joining are independent clauses.
Here’s an example where they are not.
Mike tossed the ball and watched the dog chase it.
We might be tempted to put a comma before and in this sentence, but that would be wrong. The reason for this is that the phrase: ‘watched the dog chase it’, is not an independent clause.
Comma before and in lists
We can put a comma before and when we list three or more items in a list.
For example:
My dog is obedient, affectionate, and energetic.
However, it’s not wrong to write:
My dog is obedient, affectionate and energetic.
The sentence is correct with or without the comma before and. Just remember to be consistent and don’t switch back and forth when you are writing.
You should not use a comma before and if you’re only mentioning two items and qualities. The correct way is:
My dog is obedient and affectionate.
You cannot write:
My dog is obedient, and affectionate.
For more practice, our grade 2 grammar and writing workbook provides exercises on joining two sentences with and.
