Using Commas Correctly
Solution

Comma Rule #2:
Place a comma on each side of a nonessential element.

A nonessential element is a word or phrase that provides information that is interesting and relevant but that is not essential to the basic meanng of the sentence. These nonessential elements are sometimes called "nonrestrictive elements." If the information could be left out without changing the meaning of the sentence, it is considered nonessential (or nonrestrictive). For example:

Shaquille O'Neal, who used to play for Orlando, plays for the Lakers.

In this sentence, the clause "who used to play for Orlando" is not essential to the meaning of the sentence. You could just say that "Shaquille O'Neal plays for the Lakers." Granted, the fact that Shaq used to play for Orlando is interesting and adds insight to the sentence, but it's not essential to the sentence. The sentence would not cease to be meaningful if you left that clause out. The idea here is not that you should leave out the nonessential element, but that you should place commas on either side of the nonessential element.


Here are a few more examples:

  • My cousin, who lives over on State Street, loves antique cars.
  • Sarah, my sister's best friend, drives a Mercedes.

Sometimes the nonessential element is an appositive--a word or a group of words which rename another noun. For example:
His favorite class, Biology, meets at 7:00 in the morning.
The queen, Marie Antoinette, is reputed to have said, "Let them eat cake."
In each of these two sentences, the element surrounded by commas could be removed without changing the basic meaning of the sentence. You could just say that "His favorite class meets at 7:00 in the morning" or that "The queen is reputed to have said, 'Let them eat cake.'" Again, could does not mean should, but if you could omit the element without changing the meaning of the sentence, put commas around it.


Be careful to distinguish between essential (restrictive) and nonessential (nonrestrictive) elements. If removing the element would change the basic meaning of the sentence, then it's essential and does not require commas. For example:
  • The students who succeed are those who turn in all their work on time.
  • People who volunteer with Habitat for Humanity are willing to expend significant time and energy to help others.
If you said, "The students are those who turn in all their work on time," you've changed the meaning considerably. Similarly, if you said, "People are willing to expend significant time and energy to help others," you've altered the meaning of the sentence. Because these elements are required--essential to the meaning of the sentence--they are considered restrictive and do not require commas.

Comma Rule #2:
Place a comma on each side of a nonessential element.