1) Half off/50% off 卖半价，打五折

Should I get these shoes? They're 50% off! 你觉得我应该买这双鞋子吗？打五折！

2) BOGO = Buy One Get One; two for one 买一送一

A lot of stores are having BOGO sales right now! Let's go shopping!

很多商店现在会推出买一送一的大减价！我们去逛街吧！

3) Coupon 折价券