A mass of something is a large amount of it.
许多 • She had a mass of auburn hair. 她有一头浓密的棕发。
Mass is used to describe something which involves or affects a very large number of people.
人数众多的• ...ideas on combating mass unemployment. …对付失业人数众多的方法。
When people or things mass, or when you mass them, they gather together into a large crowd or group.
聚集 There were masses of people in the shops yesterday. 昨天商店里人如潮涌。