Which order type expires at the end of the trading day if not executed?

The order type that expires at the end of the trading day if not executed is indeed a Day Order. This type of order is designed to remain active only for a single trading session. If the conditions of the order are not met by the time the market closes on that day, the order is automatically canceled.

Day Orders are commonly used by traders who want to take advantage of short-term price movements but do not wish to leave their orders open overnight or beyond the trading day. This helps to limit exposure to potential price changes and market volatility that can occur outside of regular trading hours.

In contrast, a Good-Til-Cancelled Order remains active until it is either executed or manually canceled by the trader, allowing it to carry over beyond just one trading day. Market Orders, on the other hand, are executed at the current market price as soon as possible and do not have a lifespan in the way that Day Orders do. Finally, Limit Orders specify a maximum price that the buyer is willing to pay or a minimum price that the seller is willing to accept, and they can be set as Day Orders or Good-Til-Cancelled Orders, but by themselves do not establish an expiration at the end of the trading day unless specified.