It is the quantity of a commodity specified in the contract as tradable units. The lot size is different for each commodity. The details about lot sizes / delivery lot can be obtained from the respective exchanges’ website.
Each contract has a lot size and a delivery size, which are not the same; in the case of gold, the lot size on the NCDEX is 100 gm while the delivery size is 1000 gm. If a person wants to enter into a delivery settlement for gold, he will have to enter into a minimum of 10 contracts or multiples thereof. Market participants are required to negotiate only the quantity and price of the contract, as all other parameters are predetermined by the exchange.
Please note the trading/delivery lot varies from exchange to exchange.