The convict said the judge is mad.
The convict, said the judge, is mad.
When a pause is needed in a sentence for the meaning to be clear, you probably need a comma. Many people rely on this rule of thumb entirely. However, this doesn’t always work. This handout shows the rules around comma use.
Adapted from Douglas College’s Commas without exercises
A comma is used after introductory words, phrases or clauses. Another way to look at it is that commas come before the main subject of a sentence. In this way, the comma is a sign to the reader that the main subject is coming.
Example - Words
Unfortunately, our picnic was rained out.
Example - Phrases
Laughing to himself, he drew a cartoon.
At 6:00 p.m., the family sat down to dinner.
In conclusion, the law needs to be changed.
Example - Clauses
After she finished her paper, she fell into bed and slept.
If I won the lottery, I would travel.
Because we had never met, we felt awkward at first.
She invited Amanda, Amy, Nick and Claire to her party.
Strawberries, watermelon and apricots are my favourite fruits.
A student has to go to class, take notes, read textbooks and write exams.
The shift changes at midnight, eight in the morning and four in the afternoon.
In these lists, a comma has not been used before the “and.” However, some people prefer to use commas before the “and.”
She invited Amanda, Amy, Nick, and Claire to her party.
Either with or without the comma is acceptable, however, it is good to be consistent.
A comma is used before a coordinator which joins two independent clauses. An independent clause expresses a complete thought, like a simple sentence. The only coordinators are for, and, nor, but, or, yet and so.
An excellent way to remember these coordinators is to remember the phrase FANBOYS.
FOR: They went to a fancy restaurant, for it was his birthday.
AND: He ordered salmon, and she ordered pasta.
NOR: He didn’t have soup, nor did he order anything to drink.
BUT: She wanted to have oysters, but the restaurant had run out of them.
OR: Would you like dessert, or would you prefer to get your bill?
YET: They loved the chocolate cake, yet the pieces were too big to finish.
SO: The service was excellent, so they left a big tip.
Note that the comma is optional when both independent clauses are short.
Remember that commas are used only when the coordinator joins two separate subject/verb combinations. If a sentence has one subject with two verbs, you should not use a comma.
She sat down and ordered a coffee.
Similarly, if the sentence has two subjects but only one verb, no comma is used.
The angry woman and her crying children left the store without any groceries.
When information is added to a sentence, and that information interrupts the flow of ideas of the sentence, commas are used to separate the interruption from the rest of the sentence.
Julie Payette, for example, is an excellent role model for girls.
Marc Garneau, on the other hand, is famous because he was Canada’s first astronaut.
John A. McDonald, Canada’s first prime minister, had a drinking problem.
The Justice Institute of British Columbia (JIBC) is in B.C.’s first capital, New Westminster.
A salmon, its sides gleaming, struggled up the river.
Nick, who struggled with grades in high school, is doing quite well in college.
Many downtown eastside residents use the Carnegie Centre, which sits at Hastings and Main.
To decide whether something is an interrupter, you should try taking those words out of the sentence. If you can take them out and the meaning is still clear, you have an interrupter. However, if you take the words out and the meaning is no longer clear, there is no interrupter, and you don’t need commas.
Sir Wilfred Laurier, who was a past prime minister of Canada, is pictured on our five-dollar bill.
Notice that if you take out "who was a past prime minister of Canada," the meaning of the main sentence is still clear. "Who was a past prime minister of Canada" is extra information and not essential to understanding the main sentence. Even without it, we know whose picture is on the five-dollar bill.
However, look at this sentence:
The man who lives down the street got arrested.
Notice if you take "who lives down the street" out of this sentence, you don’t know anymore who was arrested. "Who lives down the street" is needed to identify the man. For this reason, "who lives down the street" is essential information, and no commas are used.
Commas separate direct quotes from your own writing.
She said, “Pasteur really made a difference.”
“Expect snow overnight,” predicted the TV weather reporter.
“Hockey,” explained Sam, “is my favourite winter sport.”
Commas are used when you directly quote a complete idea. When only a word or phrase is quoted, you don’t need commas.
She described the television as an “idiot box.”
Commas are also not used when you report what someone said using indirect speech.
Sam explained that hockey was his favourite winter sport.
Examples - Time
January 1, 2000.
Monday, June 14, 1999.
4:30, December 31.
6:42 a.m., July 27, 1985.
Examples - Numbers
Note that commas with numbers have become optional in science and mathematics.
Example - Addresses
Moose Jaw, Saskatchewan
3652 Main Street, Vancouver
700 Royal Ave., New Westminster, B.C., V3L 5B2, Canada
Proofreading For Commas
The most straightforward way to proofread for commas is to read your text out loud. When you need to pause slightly for the writing to make sense, you probably need a comma.
However, be cautious because the over-use of commas is a more common problem than under-use.
Whenever you are in doubt about whether a comma is needed, refer back to the rules in this handout to help you make your decision.
Remember that when you have a list of two items in a list, there is not a comma before the second item.