Most difficulties with the use of the comma hinge on the distinction between restrictive and non-restrictive sentence elements.
A restrictive word, phrase or clause used as a modifier adds a “restrictive” or defining element that is essential to the meaning of the whole; it should therefore not be separated from the word it modifies by a comma or other mark of punctuation.
- The senators who had objected most strongly to the shift in policy were quick to acknowledge the error in their thinking.
(Meaning: Only some senators objected. Here, the clause “who had objected …” defines which senators were in error—i.e. the ones who objected. The clause is therefore restrictive.)
A non-restrictive element provides incidental or additional information that does not affect the essential meaning; it should be set off by a comma or commas.
- The senators, who had objected most strongly to the shift in policy, were quick to acknowledge the error in their thinking.
(Meaning: All the senators objected; the clause “who had objected …” is merely giving secondary information about all the senators rather than defining a subgroup of senators who were in error.)
Copyright notice for Writing Tips Plus
© His Majesty the King in Right of Canada, represented by the Minister of Public Services and Procurement
A tool created and made available online by the Translation Bureau, Public Services and Procurement Canada
Search by related themes
Want to learn more about a theme discussed on this page? Click on a link below to see all the pages on the Language Portal of Canada that relate to the theme you selected. The search results will be displayed in Language Navigator.
Related links
- Writing Tips Plus (home page)
- Writing tools
- Language Navigator (for fast access to language tips)
- TERMIUM Plus®