[English study] Numeral - Hundred of vs Hundreds of

When we understand the English grammar, that is sometimes hardly understandable. One of them is numeral. Most of numeral use the noun at the same time, that’s why this grammar part seems quite confusing. Be sure that you must not use the plural expression of the numeral in the noun phrase.

When you use the expression, hundred, you should not follow the normal rule to count something. For instant, when you like to express 2 hundred students.

(1) There are two hundred of students. (O)

(2) There are two hundreds of students. (X)

This is an exception of using 'hundred' expression. In this case, you don't have to add 's' after hundred, even if those are plural. However, when you like to express too many thing with 'hundred', you can use 'hundreds' of something. The third sentence can be also correct grammatically though.

(3) Hundreds and hundreds of years ago,. (O)