Large numbers

[kohyoongliat]

Large numbers of people are standing in front of the cinema.

What is the difference between 'large numbers' and 'a large number'? When should we use the former?

[rewboss]

There's no difference, but it does avoid a grammatical pitfall. Consider:

A large number of people is/are standing in front of the cinema.

"Are" here is, according to formal grammar rules, wrong, because the subject of the sentence is "a large number", which is singular. However, "is" simply sounds wrong because it comes directly after a plural noun. If you start the sentence with "large numbers", it avoids this problem.

[kohyoongliat]

Many thanks for your lucid reply.