Punctuation: The Comma

In continuation of our punctuation explanation, today we will discuss the comma. This tricky, little punctuation mark can be deceptive: It is very common, yet it must follow many specific, different types of rules. We will cover only a basic set of rules for the comma, but you will see how many different ways the comma can be used!

Commas generally have 2 different functions: to separate or to enclose. We will discuss both of these as well as a few additional conventions to remember when using the comma.

Commas That Separate

One function of the comma is to separate. This function makes perfect sense when we remember the purpose of punctuation in the first place—to make our writing more clear. When we effectively separate elements of our sentences, our writing is much easier to understand.

Independent Clauses
An independent clause is a complete thought that can stand alone. It contains a subject and a verb.

• Commas may separate independent clauses joined by coordinate conjunctions.
  Moussa wanted to leave the class early, but his teacher told him that he had to wait.
• When the independent clauses are short and closely related, the comma may be omitted.
  Moussa is eating an apple and Ernesto is eating a pear.
• Do not use a comma to separate independent clauses without a coordinate conjunction.
  Wrong  Moussa wanted to leave the class early, however, his teacher told him that he had to wait.
  Either    Moussa wanted to leave the class early; however, his teacher told him that he had to wait.
  Or        Moussa wanted to leave the class early, but his teacher told him that he had to wait.
• Do not separate compound predicates with a comma.
  Wrong     Moussa ran a mile, and lifted weights.
  Correct    Moussa ran a mile and lifted weights.

Elements in a Series

Commas are required to separate series of three or more elements.
          Jack went to the store and bought chicken, nuts, cereal, and candy.

Remember the comma that precedes the conjunction to prevent misreading.

Introductory Material

Commas may be used to separate an introductory phrase or clause from the main clause.
          While she was riding her bike to school, Jessie crashed.

• The comma is optional after a short introductory adverbial phrase unless the comma is required for clarity.
  Either       Last year, Nomen Global students went white water rafting.
  Or           Last year Nomen Global students went white water rafting.
  Wrong     Soon after Nomen Global students went to Disneyland.
  Better      Soon after, Nomen Global students went to Disneyland.

Coordinate Adjectives

Coordinate adjectives are two or more adjectives that can be linked by “and” and can independently modify the noun.

• Commas separate coordinate adjectives. To determine whether adjectives are coordinate, try inserting the word “and” between the adjectives.
  This tricky, little punctuation mark can be deceptive.This tricky and little punctuation mark can be deceptive.
  Both “tricky” and “little” independently modify “punctuation mark”.
  Compare these coordinate adjectives with non-coordinate adjectives.
  I appreciate well-prepared Italian food.“Well-prepared” modifies the whole phrase “Italian food”.

Direct Quotations

Commas separate direct quotations from the rest of the sentence.

• Separate a direct quotation or question from the rest of the sentence with a comma.
  Olivia said, “Please wash the dishes.”
• Do not use a comma to separate the sentence with an indirect quotation.
  Olivia said that the dishes need to be washed.

Commas that Enclose

Another function of the comma is to enclose. A comma that encloses requires a partner, which may be another comma or a colon, semicolon, period, question mark, or exclamation mark.

Nonrestrictive Modifiers

Commas enclose nonrestrictive modifiers. A nonrestrictive modifier does not affect the meaning of the basic sentence; it could be removed from the sentence without altering meaning.

Imagine that I have 1 sister and 3 brothers.

          My sister, who lives in Oregon, is 21 years old.

If I took out the phrase “who lives in Oregon,” the meaning of the sentence would not change.

          My brother who lives in Texas works at a bike shop.

If I took out the phrase “who lives in Texas,” the reader would not know which of my 3 brothers works at a bike shop.

Appositives

Commas enclose words or phrases in apposition unless the appositive is restrictive. A restrictive appositive is required to distinguish its antecedent from other members of the same class.

Restrictive           The precious stone sapphire is known for its blue color.

Nonrestrictive     The sapphire, a precious stone, is known for its blue color.

• The word “or” often precedes nonrestrictive appositives. The appositional “or” always requires enclosure.
  The independent clause, or main clause, must have both a subject and a verb.

Interrupting Elements

Commas enclose elements that interrupt the sentence.

                The team just lost the game. They will, however, keep practicing every day.

                Rebecca, also known as Becky, will no longer be taking classes.

Conventional Usage

The following conventional uses of the comma should be considered enclosure rather than separation.

• Dates
  This photograph was taken on January 14, 1956.
• Geographical names and addresses
  Garrett was born in Los Angeles, California, while Gordon was born in Provo, Utah.
• Numbers
  There were 37,000 people in attendance at last night’s concert.

The comma, as we said before, is a tricky punctuation mark to master; however, when you understand its functions in the sentence, the comma can be very useful.

To learn more about how and when to use commas, study with us at Nomen Global.