Commas with adjective clauses
Linguistic Reminder
(A similar problem is discussed in French in the reminder Virgule avec les relatives explicatives et déterminatives.)
Which is right: the driver, who met us at the station or the driver who met us at the station? Many people are unsure when to use commas with an adjective clause.
Solution
When deciding whether to use commas, you need to determine whether the clause is essential or non-essential.
Non-essential clause
Do use commas with a non-essential adjective clause (giving secondary information about a person or thing that is already clearly identified):
- Tommy Prince, who had extraordinary skill and courage, was descended from Manitoba's legendary Chief Peguis.
- The Bluenose, which is engraved on the Canadian dime, was a famous Nova Scotia schooner.
Essential clause
Do not use commas with an essential adjective clause (which identifies or defines a person or thing):
- Tommy Prince was a soldier who had extraordinary skill and courage.
[Tells us what kind of soldier Tommy Prince was] - The sailing vessel that is engraved on the Canadian dime is the famous schooner Bluenose.
[Tells us which sailing vessel is the Bluenose]
Tip: You don't need to use commas around an adjective clause starting with that, since it will always be essential.
Linguistic Recommendation reference number
REM-33/2011-09
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