Cách sử dụng
The expression "a straight face" means to keep a serious or neutral expression on your face despite feeling amused, surprised, or angry. You can use this expression when you are talking about situations where someone is trying to hide their true emotions, like a poker player who keeps a straight face when they have a good hand. You can also use this expression if you want to give someone a warning not to joke around in a serious situation, like telling a friend to keep a straight face when talking to their boss.