deep down

Từ điển Oxford Advanced Learner 8th

deep ˈdown idiom
1. if you know sth deep down, you know your true feelings about sth, although you may not admit them to yourself
•Deep down I still loved him.
2. if sth is true deep down, it is really like that, although it may not be obvious to people
•He seems confident but deep down he's quite insecure.
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