Commas around extra information
Extra information that could be removed goes between two commas, or none at all.
Updated October 29, 2026
The rule
If a phrase adds detail but the sentence means the same without it, set it off on both sides: "My brother, who lives in Ohio, is visiting." Forgetting the second comma is the most common mistake.
If the phrase tells you which one, it is essential and takes no commas: "The student who won the race shook hands."
Examples
My aunt, a pilot flies to Rome every month.My aunt, a pilot, flies to Rome every month.The book, that I borrowed, is overdue.The book that I borrowed is overdue.
Quick test: Lift the phrase out. If the sentence still makes sense and means the same, it needs a comma on each side.
Try it: find the mistake
The mistake in each sentence is highlighted. Say the fix out loud, then open the answer.
Mr. Lopez, our neighbor fixed the fence.
Mr. Lopez, our neighbor, fixed the fence.
"Our neighbor" is extra information. It opened with a comma, so it must close with one too.
The Nile which is the longest river in Africa, flows north.
The Nile, which is the longest river in Africa, flows north.
"Which is the longest river in Africa" is extra, so it needs an opening comma to match the closing one.
My cousin, who lives in Texas is visiting us.
My cousin, who lives in Texas, is visiting us.
"Who lives in Texas" is extra information. It opened with a comma, so it needs a comma to close it.
The students, who studied, passed the exam easily.
The students who studied passed the exam easily.
This tells which students passed, so it is essential and takes no commas.
Where this rule is tested
Questions people ask
What is the rule for commas around extra information?
Extra information that could be removed goes between two commas, or none at all. If a phrase adds detail but the sentence means the same without it, set it off on both sides: "My brother, who lives in Ohio, is visiting." Forgetting the second comma is the most common mistake.
How can I check my commas around extra information quickly?
Lift the phrase out. If the sentence still makes sense and means the same, it needs a comma on each side.
Where can I practice this for free?
In Owl Test Prep's Daily Grammar Fix: one sentence a day for everyone, plus practice sets of five on this rule. It is free, with no account.