The answer. The main contract refers to the contract with the largest turnover. Because it is the most active contract in the market, basically all speculators are participating in this contract. It is also said that the main contract is the contract with the largest position, because generally speaking, the contract with the largest position is also the contract with the largest turnover.

Expand. The full name of stock index futures is stock price index futures, which can also be called stock index futures and futures index. It refers to the standardized futures contract with the stock index as the subject matter. The two sides agreed that on a specific date in the future, they can buy and sell the underlying index according to the size of the stock index determined in advance, and then settle the difference in cash after the expiration.