An appositive is a noun that is placed after another noun in order to tell more about it and it's usually set off with commas.

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That's correct! An appositive is a noun or noun phrase that provides additional information about another noun preceding it. It helps to clarify or further describe the noun. Appositives are typically set off by commas to separate them from the rest of the sentence. This punctuation helps to indicate that the appositive is non-essential and can be removed without fundamentally changing the meaning of the sentence.

To identify an appositive in a sentence, follow these steps:

1. Look for a noun or noun phrase that appears immediately after another noun.
2. Determine whether the appositive is essential or non-essential by removing it from the sentence and observing if the meaning changes significantly.
3. If the appositive provides crucial information, it is an essential appositive and shouldn't be set off by commas. If the appositive provides extra, non-essential information, it is a non-essential appositive and should be surrounded by commas.

Here is an example:

"The dog, a golden retriever, played in the park."

In this sentence, "a golden retriever" is the appositive because it follows "the dog" and provides additional details about it. Since the phrase is non-essential and can be removed without altering the meaning of the sentence, it is set off with commas.