Writing · Commas
Add or remove commas where necessary. Some sentences contain restrictive clauses that need no commas; others contain non-restrictive information that must be set off with commas. If a sentence is already correct, rewrite it unchanged.
About This Rule
- A restrictive (essential) clause or phrase identifies which person or thing you mean. Without it, the meaning changes, so it takes no commas: Students who excel in academics often receive scholarships.
- A non-restrictive (non-essential) clause or phrase adds extra information about something already identified, such as a named person or place. Set it off with commas: McGill University, founded in 1821, is located in Montreal.
- Clauses with that are always restrictive. In American English, which usually introduces non-restrictive clauses.