Of all punctuation marks in the English language (and all languages, for that matter), the comma is by far the most difficult to master—it’s also at the core of much debate. For instance, must we place a comma before the final and or or in a series of three items or more? Debates surrounding the serial or Oxford comma are endless; some see the comma before a coordinating conjunction as useful for clarity. Others, however, may perceive the serial comma as unnecessary because it clutters texts.
I’ll save the serial comma debate for a future entry. Here’s a more down-to-earth question: Is the comma necessary in every sentence we write? Not necessarily, especially if we consider that sentences can either be non-restrictive or restrictive in nature.
“Wait, what? A non-restrictive or restrictive sentence? What are those?” you may be asking yourselves.
Simply put, non-restrictive sentences contain elements that are considered non-essential to the overall sentence. These non-essential elements are set off by commas.
The company, which is located in Newfoundland, has an excellent reputation. 
The Air Canada Centre, located in the heart of downtown Toronto, attracts several tourists each year.
Michael Ondaatje’s fourth novel, The English Patient, won the Booker Prize. 
The italicized elements indicate non-essential information that can be removed without significant loss of meaning. Without this information, the sentences read:
The company has an excellent reputation.
The Air Canada Centre attracts several tourists each year.
Michael Ondaatje’s fourth novel won the Booker Prize.
All sentences are grammatically correct, even though parenthetical information has been removed.
In contrast, restrictive sentences contain elements considered essential to the overall sentence. Because information is considered essential, said sentences cannot be set off by commas.
People sitting in the rear couldn’t hear. 
The novelist Margaret Laurence wrote The Stone Angel. 
George Frideric Handel composed the sacred oratorio Messiah in 1741.
Try setting off these sentences with commas. Would the sentences make sense?
People, sitting in the rear, couldn’t hear. (Read: “People couldn’t hear.” What could people not hear? Where were they when they couldn’t hear?)
The novelist, Margaret Laurence, wrote The Stone Angel. (Read: “The novelist wrote The Stone Angel.” What novelist are we talking about?)
George Frideric Handel composed the sacred oratorio, Messiah, in 1741. (Read: “George Frideric Handel composed the sacred oratorio in 1741.” What oratorio are we referring to?)
As you can see, setting off restrictive elements with commas makes sentences hard to understand.
In the second example, Margaret Laurence specifies what novelist we are talking about; therefore, it is impossible to set off the novelist’s name with commas.
If you’re a classical music fan like myself, you may have balked at the last sentence. If you offset Messiah with commas, you are wrongly suggesting that Handel composed only one sacred oratorio. The truth is, Messiah was one of many sacred oratorios composed during the composer’s lifetime. At last count, he composed 27 of them.
Conclusion: If elements of a sentence cannot be removed without a significant loss of meaning, you have a restrictive sentence. By the way, Junior (abbreviated Jr.) is a restrictive element.
Eugene Taylor Jr. (not Eugene Taylor, Jr.)
 H. Ramsey Fowler et al., The Little, Brown Handbook, 6th ed. (Toronto: Pearson Canada, 2011), 390.
 Ibid, 393.
 William Strunk Jr. and E.B. White, The Elements of Style, 4th ed. (New York: Longman Publishers, 2000), 4.
 Catherine Cragg et al., Editing Canadian English, 2nd ed. (Toronto: McClelland & Stewart Ltd., 2000), 60.