Contract size refers to the quantity of the underlying asset that is associated with a single derivative contract. For example, in the case of futures, the contract size represents the amount of the underlying asset that a futures contract represents. It is the standardized unit of measurement that determines how much of an asset is represented by a single contract. The contract size can vary widely depending on the type of financial instrument and the exchange on which it is traded. The contract size is an important consideration for traders, as it can affect the amount of capital required to trade a particular instrument and the level of risk associated with a trade.