An appositive is a noun or noun phrase that modifies or explains another noun. The appositive comes immediately before or after the noun it modifies. Here are some examples. (The appositive appears in bold text.):
My friend Marie is studying psychology.
“Marie” explains who “my friend” is.
John’s father, a truck driver, spends many hours on the road.
“A truck driver” clarifies why “John’s father” spends so much time on the road.
Angela went to lunch with her coworker Justin.
The appositive gives us the name of Angela’s “coworker.”
Appositives before Nouns
An appositive usually follows the noun it modifies, as in the previous examples. However, you can place the appositive before the noun it describes as well. For example:
A natural athlete, Mark plays soccer, football, and baseball.
A leading expert in her field of study, Jennifer is often asked to speak at anthropology conferences.
Whether you place the appositive before or after the noun it modifies is basically a style choice. Placing the appositive after the noun generally produces a smoother-flowing sentence, but this is not always the case. The appositive phrase in the first example would sound like it was interrupting the sentence if you placed it after the person’s name.
When an appositive is essential to the meaning of the noun it modifies or the meaning of the sentence as a whole, do not enclose it in commas. A restrictive appositive narrows (restricts) the meaning of the noun it modifies. Here’s an example:
The controversial singer Lady Gaga wore a gown made of toilet paper to the Grammy Awards.
The appositive tells us the name of the “controversial singer.” The sentence still functions without “Lady Gaga,” but it’s not very descriptive if you remove the appositive. Lady Gaga has a reputation for wearing attention-getting outfits. A toilet paper dress is consistent with her public image.
On the other hand, you should use commas when you include an appositive that is not essential to the meaning of the noun it modifies. Let’s flip the restrictive appositive example around so that “Lady Gaga” is the subject and “the controversial singer” is the appositive:
Lady Gaga, the controversial singer, wore a gown made of toilet paper to the Grammy Awards.
Now “the controversial singer” provides additional information about who “Lady Gaga” is. Since a reader could reasonably infer that an artist known for such wardrobe choices might create controversy, you need to frame the appositive with commas.