What is an appositive?

An appositive is a noun (or noun phrase) that provides information about another noun.

Appositive:

The man of the hour, Mr. Shoemaker, took his place at the podium.

At the end of the aisle I saw my mother, Ruth, coming toward me.

Appositive Phrases:

A big fan of country music, Sarah was excited to go to the Taylor Swift concert with her friends.

Martha, a gifted artist as well as a patron of the arts, pledged her support of the new gallery.

Her father’s underlying goal, to prevent his daughter’s marriage, was behind his decision to expose the family’s secret.

What is the proper way to punctuate appositives?

The general rule for punctuating appositives and appositive phrases is simple.

If the information is essential to the meaning of the sentence, do not use commas to set it apart:

            In my apartment complex, my neighbor Sam is the most quiet.

For this example, “Sam” is essential to the meaning of the sentence. There are presumably other neighbors, and only one of them is the most quiet.

If the appositive provides extra (nonessential) information, use commas to punctuate it:

In my apartment complex, the landlord, Robby, keeps things neat, tidy, and under control.

For this example, there is only one landlord, and his actual name is nonessential.

One more example of appositives and their proper punctuation:

Mark’s brother Kurt and his wife, Christine, were the only members of his family to show up at his graduation ceremony.

From this sentence we learn that Mark has more than one brother, making identifying the brother by name a necessity, and only one wife—we hope—whose name is nonessential and therefore set off by commas. (Don’t tell his wife.)