If you pay close attention to written greetings, you'll notice a difference in how people punctuate them. Some include a comma after the greeting word (Hi, Bob), while others skip it (Hi Bob). Sometimes it depends on the greeting word (Hi Kate but Hello, Kate), the register (Hello honey but Hello, Dr Smith), or things like mood and whim. So what are the rules for this erratic mark? The comma in question is called the vocative comma, because these structures are in the vocative case. The word has the same Latin root as vocation and shares its sense of 'calling'. The vocative comma is used in many more situations than just greetings: Yes, your honour. Good night, love. Thanks, buddy. Et tu, brute? Happy new year, everyone! Tell me more, Stan. The purpose of the vocative comma is to separate the person or thing being directly addressed from the rest of the line. That means it doesn't always precede the addressee – it can also follow them: Anne, look at this. Ladies and gentlemen, you're