Direct Address and Interjections
Sometimes a sentence will address a person spoken to by name or will contain an interjection, a word or sound that expresses a feeling or is used to get someone’s attention. Neither nouns in direct address or interjections are felt to be part of the sentence structure, and both kinds of expressions, italicized in the following examples, are set off from the rest of the clause by commas:
Please, Mr. Fang, take your tooth from my wrist.
Your Majesty, we all wish to thank you for that beautiful tap dance.
Hey, can we have a little less writhing around here!
Yes, I believe cobras are sensitive.
Note the difference between “Dear Lora” and “Hi, Lora.” Dear modifies Lora (no punctuation), while hi is an interjection.