I read that when you classify or define people and things you use a/an:
Don't use your plate as an ashtray.
But then I found a news article which included the following sentence:
Indian teenager allegedly raped twice after cops failed to follow her after using her as 'bait'.
Shouldn't the correct sentence be "using her as a bait?"
My question is as follows:
Which is grammatically correct? Using her as bait or using her as a bait?
If the former is correct then why is the indefinite article not used after as? Isn't it defining her as a bait?
If both are grammatically correct then what is the difference in meaning or usage?
Any help would be greatly appreciated.