Commas are used to separate parts of sentence in order to mark some of the pauses made in speech.
We use commas :
- Before “and” to make meaning quite clear.
I study Mexican poetry, and painting.
I study Mexican poetry and painting (no comma because both are Mexican).
- Sometimes before “or or nor” in order to make meaning clear.
Work hard, or you’ll fail (Comma is necessary).
David or Ken will clean the board (no comma).
- Usually before “but”.
The room was hot, but clean.
We kept knocking, but nobody opened.
- Always before “for”, “as” and “since” (when these mean because).
There was no need for me to get dressed, for I was not invited.
- to separate phrases.
If you work hard, you’ll succeed.
When Martin comes, ask him to phone me.
- before and after a clause or phrase that gives additional information.
Adina, whose mother is Mexican, speaks both English and Spanish.
- to separate a tag question from the rest of the sentence.
He lives in Ankara, doesn’t he ?
She is Romanian, isn’t she ?
- to separate words in a list, but they are often omitted before “and”.
I bought flour, eggs, butter and two bottles of milk.
I am with Shana, Dana and Joshua.
- before “said” when writing down a conversation.
“Don’t be late”, She said.
“She’s a beautiful lady !”, Alain said.