A vocative comma sounds like something that sends people scurrying in terror to dusty Latin textbooks, but it is really quite straightforward.
Put simply, the vocative case is used to address a person (or if you’re feeling in a more poetic frame of mind, a place or an object).
In languages like Latin the vocative case would involve changes to the endings of nouns and various other tortures. In fact, it still exists in Irish and Scots Gaelic, which is why the name Seamus is pronounced as Hamish when shouted out in greeting on country roads on bright spring mornings.
But in English we can simply mark the noun off with commas; job done.
Finally, we’ve found a job that the comma can do with no fuss and even less confusion.
Examples of vocative commas
John, can you pass me that red pencil?
It’s about time, Chris, that you began to take commas more seriously.
Does this sentence look alright to you, Maggie?
Missing a vocative comma
The importance of the comma becomes more obvious if we look at a couple of alternatives.
I don’t know, John.
has a very different meaning to
I don’t know John.
While the first example involves someone confessing to John that they do not know, the second example shows that they don’t even know John himself.