One Comma or Two? Why?

I love the picture above, and although it may not seem to connect with showing us some American punctuation rules … it actually does for many rules, especially commas.

There’s a rule that says where we need TWO commas – never just one – and luckily it’s the easiest rule to understand.

Start with this: Most of us know how to use parentheses, right? We use them to enclose extra stuff that’s good to know but could easily be left out of a sentence without major loss of understanding. And the sentence would still work grammatically.

Oh, you didn’t know all that? Well, OK. But that’s why we use ( ) – to show stuff we think a reader will benefit from knowing but doesn’t NEED to know to make sense of the sentence.

Example: Susan has lived in Buzzards Bay (Mass.) for four years.

Could that sentence be written without Mass.? Um, yup. Would it still work as a sentence? Yup again. Does having Mass. in it help a little more? Yes. But it’s not ESSENTIAL, which is the word most often used when describing this kind of information. Good to have but not essential.

I can hear you now! “Susan! I would want to know where the heck Buzzards Bay is!”

Sure, but you don’t NEED to. No matter what, you still know I live in Buzzards Bay.

Of course, you can always put in the nonessential info, either enclosing it with parentheses or TWO commas.

You knew we’d get to the commas …

The “why” of the two commas is simple: The parenthesis mark is made up of two parts: the ( and the ). But because parentheses are large and often draw a reader’s eyes towards information the writer has decided is nonessential – the reader may focus on the wrong stuff.

So, what’s the cure? Since parentheses basically enclose the information, we need to use two commas to mimic the ( ), one before the information and one after it, exactly where each half of the parenthesis mark would be.

Example: Susan has lived in Buzzards Bay (Mass.) for nearly four years.

Example: Susan has lived in Buzzards Bay, Mass., for nearly four years.

Example: Susan has lived in Buzzards Bay (a section of Bourne, Mass.) for four years.

Example: Susan has lived in Buzzards Bay for nearly four years.

I much prefer adding the nonessential info, when I can and when I have enough space, preferably using commas because they are small and don’t draw a reader’s eyes away from the whole sentence. 

Does this help at least explain the why of using two commas sometimes?

FYI: Buzzards Bay is a district of Bourne, so I could say I live in Bourne. But the name Buzzards Bay just cracks me up. The name was given to this bay by colonists who saw a large bird that they called a buzzard near its shores.