The Use of the Comma
- To separate a vocative from the remainder of a sentence:
Patricia, we very much doubt whether it can be done.
- To separate a parenthetical clause from the remainder of a sentence:
Arthur, absent-minded as usual, had forgotten the invitation.
- To separate direct speech from its reporting verb and other words:
"Sit down", she said quietly, "and listen to what I have to say."
- To separate items in a list of enumeration:
Robert ordered half a loaf of fresh bread, some local butter, some cheese, a large onion, and a pint of beer. (the final comma can be omitted)
I don't know when he will come, how he will come, with whom he will come, or whether he will come at all!
BUT somethimes the presence or absence of a comma changes completely the meaning of a sentence:
The twins, Mary and Helen, went home early. (two people)
The twins, Mary, and Helen went home early. (four people)
Let's eat grandpa!!!
Let's eat, grandpa.
- To separate an adverbial clause from a main clause:
As soon as he arrives, give him this note.
If you want any help, just let me know.
- To distinguish a non-defining (parenthetical) relative clause from a defining one:
The animals, which had not been brought under cover, were killed by the sub-zero temperatures. (= all the animals)
The animals which had not been brought under cover were killed by sub-zero temperatures. (= only some animals - the ones that had not been brought under cover)
- After each of two or more adjectives or prepositions:
She is a clever, but a self-opinionated, woman.
- To indicate the omission of a part of a sentence:
Molly and Carol will go with Philip in the Mazda; you and John, with me in the Bentley!
(omitted: will go)