Good for day is a type of order in financial markets that is valid only for the current trading session. It means that if the order is not filled by the end of the trading day, it will automatically expire and will need to be re-submitted if the trader wants to place the same order the following trading day. This type of order is commonly used by traders who want to specify a specific price level at which they want to enter or exit a trade, but only for a limited time frame. It provides traders with a greater degree of control over their orders and helps to limit the potential risk associated with market fluctuations.