essence：the most basic and important quality of something
The essence of Macau is poker chips and entertainment.
如果将“poker chips and entertainment”看作是一个整体，谓语动词就用单数；如果看作两个个体，就可以用复数。
The essence of various cryptocurrencies is blockchain technology.
1）The essence of startups is rapid growth.
The essence of start-ups is scalability/rapid growth.
2) The essence of a student is to acquire knowledge and make preparations for going into the society.
