1. 不开心:unhappy;upset;sad。
2. 我没有察觉到你那么不开心。I didnt realize you were so unhappy。
3.我没有察觉到原来他那时很不开心。I didnt realize but he was deeply unhappy at that time。
4. 别让他搞得你一晚上不开心。Dont let him spoil your evening。
5. 他在新老板的手下工作得很不开心。He was chafing under the companys new ownership。
6. 事实明摆了，他就是不开心。The bald truth is hes just not happy。