This is the 1894th most frequent Chinese word.
后悔
Regret.
后悔 is used here as a verb expressing emotions over a past event.
他感到非常后悔，错过了一个重要的机会。
He feels very regretful for missing an important opportunity.
后悔莫及 is a phrase using 后悔 to intensify the feeling of regret being beyond remedy.
这个决定让我后悔莫及。
This decision left me with great regret.
后悔 is used to denote a lack of remorse or regret for her own actions.