Resources – Common Comma Errors
Introduction to the Topic
Next to the period, the comma is the most frequently occurring punctuation mark, but often the most easily misunderstood and misused. Take my last sentence, for example. Is a comma necessary between “mark” and “but?” Is there a rule stipulating the use of a comma there? If there is not a rule, can I include a comma between these two words so that I can signal to my reader to take a pause? In this blog post, we’ll walk through some of the most common comma mistakes and explain the underlying rules for them.
The Five Most Common Mistakes
Mistake #1: No comma after an introductory element
Example: “When I need to look up directions I can use Google Maps online.”
Correct version: “When I need to look up directions, I can use Google Maps online.”
In the above sentence, “I can use Google Maps online” is the main, independent clause in the sentence. An independent clause is a clause that has a subject and a verb and could stand alone as a sentence. Oftentimes, an introductory phrase precedes the main clause of the sentence and tells the reader information regarding the circumstances—when, where, how, why, etc.—under which the main action occurred. A comma is necessary to separate the introductory element from the main clause. An exception to this rule is that a comma is not needed after a short introductory element when a misreading is unlikely. (For example: “Before soon we had arrived at the airport.”)
Diana Hacker, The Bedford Handbook For Writers, 4th ed. (New York: St. Martin’s Press, Inc., 1994) 351.
Mistake #2: No comma in a non-restrictive element
Example: “My car which is a Toyota Camry ran out of gas last night.”
Correct version: “My car, which is a Toyota Camry, ran out of gas last night.”
The main purpose of the sentence above is to tell the reader that the writer’s car ran out of gas last night. It’s not essential to the meaning of the sentence that the car was a Toyota Camry. The car could have been a Ford Focus or a Chevy Silverado—what’s important is that the car ran out of gas. In this example, the phrase “which is a Toyota Camry” is a non-restrictive element because it does not define or limit the meaning of the word it modifies (car).[2] Non-restrictive elements are signaled by a comma and often by a relative pronoun following the comma. “Which” is the most common relative pronoun used to set off a non-restrictive element, but others include who, whom, and whose.
Diana Hacker, The Bedford Handbook For Writers, 4th ed. (New York: St. Martin’s Press, Inc., 1994) 356.
Mistake #3: Unnecessary comma with a restrictive element
Example: “The parents chose to send their child to the neighborhood school, which had the best math program.”
Correct version: “The parents chose to send their child to the neighborhood school that had the best math program.”
In the above sentence, it was essential to the parent’s decision on a neighborhood school that it had the best math program. Merely stating “The parents chose to send their child to the neighborhood school” doesn’t have nearly the amount of meaning that the writer intends to convey. Clauses that are essential to the meaning of a sentence are labeled restrictive—that is, they restrict, or affect, the meaning of the sentence. “That” is always used to signify a restrictive clause, and a comma never precedes “that.” A test to see if an element is restrictive is to remove it from the sentence and ask, “is my sentence too general now?” If yes, then the removed element was probably restrictive. You want to keep it in the sentence, uninhibited by a comma.
Mistake #4: No comma in a compound sentence:
Example: “George travelled to Hawaii and he enjoyed meeting many people.”
Correct version: “George travelled to Hawaii, and he enjoyed meeting many people.”
Clauses can be categorized in two main categories: independent or dependent. An independent clause is one that can stand alone and has a subject and verb. Sometimes sentences have two or more independent clauses, and these sentences are compound sentences. In order to separate two independent clauses, a comma followed by a coordinating conjunction is needed. The English language has seven coordinating conjunctions. You can easily memorize these conjunctions with the following acronym: FAN BOYS (for, and, nor, but, or, yet, so).
Mistake #5: Comma Splice
Example: “My roommates are not very tidy they also make way too much noise at night.”
Correct Version #1: “My roommates are not very tidy, and they also make way to much noise at night.”
Correct Version #2: “My roommates are not very tidy. They also make way to much noise at night.”
A Comma Splice occurs when only a comma separates two independent clauses. In the sentence above, both clauses referring to the roommates’ untidiness as well as their rowdiness can stand alone. When two independent clauses appear in a sentence, a comma followed by a coordinating conjunction is one way to solve the comma splice problem (listed above). The two clauses can also be turned into separate sentences by adding a period. Either way, a writer’s ideas will be expressed more clearly.
– Developed by Adam Dominik & Lauren Rodosky
