An appositive phrase contains nouns or pronouns that are placed beside and clarify other nouns or pronouns, states the Purdue Online Writing Lab. An example of an appositive phrase placed at the beginning of a sentence is, "Always the consummate professional, Bill received the boss's negative feedback and improved his performance."
"The charismatic pop singer Michael Jackson left a lasting legacy" is another example of an appositive phrase at the beginning of a sentence. In this example, the appositive phrase preceding "Michael Jackson" is not followed by a comma because the phrase contains information that is essential to the basic meaning of the sentence. Conversely, "Michael Jackson, the charismatic pop singer, left a lasting legacy" contains the appositive phrase surrounded by commas because it is not essential to the basic meaning of the sentence. As Purdue Online Writing Lab clarifies, when the appositive phrase is not essential, the reader still knows who the subject of the sentence is.
Other examples of appositive phrases include, "The popular physician Dr. Alicia King went on a vacation" and "The lawyer, who was an expert in criminal law, had three legal assistants." In the first sentence, Dr. King is preceded by the appositive phrase describing one of her characteristics. In the second example, the appositive phrase in commas is unnecessary to the basic meaning of the sentence and clarifies an incidental fact related to the lawyer.