A vocative expression
is an expression of direct address, wherein
the identity of the party being spoken to is set forth expressly within a
sentence. For example, in the sentence, "I don't know, John.", John
a vocative expression indicating the party who is being addressed.
Some languages (e.g., Greek) have a special vocative case for this; others do not. English simply uses the subjective case
for vocative expressions but sets them off from the rest of the sentences
with pauses (rendered in writing as commas).
A vocative expression is interjective and can occur in any clause, irrespective of mood. Some examples...
- Good morning, class!
- Don't forget your swimming trunks, George.
- Hey, George, did you remember to bring your swimming trunks?
- No, Bob, I forgot.
- I'm proud of you, son.
- If I were you, Mary, I'd take French next year instead of Spanish.