According to most English textbooks and instructors, the omission or misuse of commas is the #1 sentence-level error in writing. Many beginning writers overlook the importance of a correctly used comma, or insert commas as an afterthought where they think they need a pause. Commas, like any punctuation, have rules of use, and failing to follow the rules can lead to, what may appear in your sentence, to be death – or just really awkward and embarrassing sentences!
As the title of this post illustrates, a missing comma can alter the meaning of an otherwise straightforward sentence. With a correctly placed comma,
Let’s eat, Grandma.
it’s understood that we don’t really want to eat Grandma, but that someone is requesting that Grandma eat.
A comma prevents readers from grouping words together in ways that don’t fit your intended meaning, as in the following example:
Did the bear eat John?
I hope not! With a comma, we’re asking John if the bear has eaten:
Did the bear eat, John?
In the following example of a missing comma, you can see how it could create a disturbing image:
All those who like to cook and eat my wife just started a new blog.
There must be a lot of people who like to cook and eat this person’s wife!
With comma: All those who like to cook and eat, my wife just started a new blog.
Comma in a List of Items
What’s for Dinner?
Your mother is making broccoli chicken, peas, and carrots for dinner. So is she making one entrée and one side dish? Or is she making one entrée and two side dishes? Or two entrées and two side dishes? Confused? You might have an idea what food you will be eating, but unless you understand how the sentence is punctuated, you might not know how to interpret the menu.
In the example, broccoli chicken has no comma to separate the words, so it is one dish, like they serve at the corner Chinese restaurant. But peas and carrots are separated with a comma, which indicates that instead of one side dish of mixed peas and carrots, you’ll get a side of peas, and a side of carrots. Make sense? Punctuation can change the meaning of your sentences, and if you’re not careful, you might say something you don’t really mean.
While we’re on the subject of eating, the following faux pas was printed on a magazine cover:
Rachel Ray finds inspiration in cooking her family and her dog.
I doubt Rachel Ray has cooked her family or her dog! Once we add the missing commas in this list, we’re relieved:
Rachel Ray finds inspiration in cooking, her family, and her dog.
That sounds better, doesn’t it?
Below is another example of how failing to place commas in a series can have shocking effects:
Caution! Watch for parasailing horses and buggies on the beach.
I’ve never seen that, have you? But there still seems to be some confusion.
Notice the item – or items – “horses and buggies.” Without a comma to guide us, we don’t know if “horses and buggies” are one unit together like this:
or if they are two separate entities, like this:
Commas have rules of usage. There should be no guessing when or where to use any kind of punctuation. Feeling the need to take a breath or pause in a sentence does not necessarily mean you need a comma, but a comma does mean you need to pause.
Now go eat, Grandma!
(Some examples from http://www.ucalgary.ca/uofc/eduweb/grammar/course/punctuation/3_4j.htm)