Written by Jincy Kornhauser at Pearson Tutor Services
Comma usage is a thorny issue for many writers because the rules can seem so bewildering. Writers who give up trying to understand them will often resort to sticking in commas whenever a sentence seems to be going on too long, in hopes that at least some of the commas will be correct, because you can never have too many commas! Unfortunately, you can, and the incorrect use of a comma does as much damage to the flow of a sentence as a missing comma does. Let’s clear up some confusion.
There are two basic uses of commas: to divide items in a list of 3 or more, and to set off material that is not strictly necessary to the meaning of a sentence.
1. Here are some list-separating commas:
I can’t bake a cake without flour, sugar, eggs, and unsweetened chocolate.
Henry ran to the cupboard, grabbed a stack of plates, headed back to the dining room, bumped his elbow on the doorframe, and dropped the whole stack on the hardwood floor.
Note that in each sentence there’s a list of 4 (in the first sentence, it’s a list of things; in the second it’s a list of predicates; it can be a list of anything) and that a comma separates them from one another. This makes the sentence easy to organize and read. The second sentence would be a real nightmare without those divider commas!
2. Here are some “setting off” commas:
I prefer to use Beauzeau Cocoa, a premium chocolate powder imported from Mozambique, to make devil’s food cake.
Henry, who is the clumsiest person I’ve ever met, has smashed twelve plates and a soup tureen since he came to work for us.
In each case the material enclosed in commas—while contributing information to the sentence—is not essential to the sentence. Here’s proof:
I prefer to use Beauzeau Cocoa to make devil’s food cake.
Henry has smashed twelve plates and a soup tureen since he came to work for us.
When we lift the material out of the sentence, the sentence is still meaningful. The two commas act like basket handles: they show us where the non-essential material begins and ends, and we can use them to lift that material up and away, leaving the essence of the sentence behind.
In other words, divider commas come in singles, while setting-off commas come in pairs.
Of course, it’s a bit more complicated than that, since not all non-essential material is placed in the middle of a sentence. Often it comes at the beginning:
Although he’s our clumsiest employee, Henry Mudge gets along wonderfully with the guests.
Note that “although he’s our clumsiest employee” could be placed in the middle of the sentence (after “Henry Mudge”) and enclosed in commas. But here it begins the sentence, so only one comma is needed.
Sometimes it comes at the end:
Last night we awarded the Problematic Employee of the Month award to Henry Mudge, our beloved yet bungling waiter.
Again, the sentence could be revised (Henry Mudge, our beloved yet bungling waiter, has been awarded the Problematic Employee of the Month award) so that the non-essential material is enclosed in commas.
In other words: “basket handles” can consist of a comma paired with an end-of-sentence period, or a sentence starting-point paired with a comma, or two commas.
So: When looking over your sentence to decide where (or if) to place commas, first look for lists of three or more. Then look for phrases and clauses that are not necessary to the meaning of the sentence—passages which could be lifted out without harming the sentence’s basic meaning. If you find one, give it basket handles.
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