In trading, a lot refers to a standardized quantity of a financial instrument that is traded. For example, in the forex market, a standard lot is typically 100,000 units of the base currency. However, there are also other lot sizes, such as mini-lots and micro-lots, which are 10,000 units and 1,000 units respectively. In other markets, such as the stock market, a lot may refer to a specific number of shares that are traded together, often in multiples of 100.