A comma is used as an interrupter in the following three ways:
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Direct address - A comma is used to separate the name of the person being addressed from the rest of the sentence. For example: "Let's eat, Grandma!"
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Parenthetical expressions - Commas are used to enclose phrases that provide additional information but are not essential to the main point of the sentence. For example: "The car, if you can believe it, has over 200,000 miles on it."
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Appositives - Commas are used to set off appositives, which are nouns or noun phrases that rename or provide further details about another noun. For example: "My brother, an avid sailor, just bought a new boat."
These uses of commas help clarify meaning and add extra information to sentences.