Dear sir,

I have recently come across a few instances of the phrase "a large
numbers of ..." being used in sentences, supposedly written by native
english speakers. I have always thought that "a large number of ..."(with out 's')
is the only correct expression. My questions then are:
1. Is the phrase "a large numbers of ..." used?
2. And if so, how is it different from "a large number of ..."?

Thank you very much
You cannot say "a large numbers" This is bad English. If you use "a" you are refering to the singular. You must say, "a large number."

You can say, "large numbers of..."

"Large numbers of tourists came to China in 2002."

Or you can say, "

"There was a large number of tourists in the Forbidden City last year."
Thanks Emotion: wink