Identify the appositive in the following sentence.
the building, a tall, gray structure, sat abandoned near the freeway.
the building
a tall, gray structure
sat abandoned near the freeway

a tall, gray structure

Explanation:

An appositive phrase is a noun or a noun phrase that renames, identifies or gives further information of another noun that is right beside. This type of phrase can be either restrictive (when it's essential to the meaning of the sentence) or nonrestrictive (when it's not essential to the sentence, and therefore should be set off with commas, dashes or brackets).

In the sentence, "A tall, gray structure" is the appositive phrase as it is a noun phrase that gives further information to the noun "building", it is right beside that noun and is set off by commas (which means that it is also a nonrestrictive one).