Commas before Conjunctions

Newsroom101

Commas before Conjunctions in Compound Sentences

The basic rule: When two complete sentences are joined by a conjunction (most often and, but, or or), place a comma before that conjunction.

Note the commas in the following examples. The complete sentences are underlined.

We arrived early, and no one else was there.
We looked through the church, but we did not see anyone.
We could wait to see if anyone else came, or we could go back home.

Each of these is a "compound sentence" consisting of two complete sentences or "independent clauses."

Less-Common Conjunctions
The same rule holds for the words for, nor, so, and yet, when they are used as conjunctions.

We wanted to leave, yet something held us there.
We didn't know what to do, so we sat down to wait.
The place made me uncomfortable, for it was cold and damp.
The others would not leave, nor would they wait outside with me.

These conjunctions are less common in journalistic writing, especially "nor."

Note: Omitting the comma before this conjunction is one of the 20 most common grammatical errors.

But don't use a comma with a compound verb:

We looked through the church and searched outside the building. [no comma]

Compare this compound sentence:

We looked through the church, and we searched outside the building. [comma before "and"]

Note the difference (and the comma):
Sentence 1: We looked and searched.

"We" followed by the compound verb "looked and searched."

Sentence 2: We looked, and we searched.

Two independent clauses: "We looked. We searched." Joined by "and," with the help of that independent punctuation mark, the comma.

Practice using a comma in a compound sentence.