Why is もの in this sentence?

Question

What's its role in the sentence below?

クラスのもの皆が彼の冗談に笑った。

Answer 1

It's 者【もの】, a word that means "person/people".

Unlike 人, it's usually used as part of a compound word (eg 田舎者), or at least modified by another word/phrase. It's also often used as the humble word for 人, which is not the case with your example.

See: Difference between 者{もの} and 人{ひと}