relapse
verb [ I ] formal uk/rɪˈlæps/ us/rɪˈlæps/
（病好转后）复发；故态复萌；重新堕落
to become ill or start behaving badly again, after making an improvement
She managed to stop using drugs for a month, but then relapsed. 她坚持了1个月没有吸毒，但是接着又故态复萌。
He looked happy for a brief while, before relapsing into silent misery. 有那么一阵子他看上去很幸福，但接着又陷入了无言的苦恼中。
relapse
noun [ C ] formal uk/ˈriː.læps/ us/ˈriː.læps/
旧病复发
If someone who is getting better after an illness has a relapse, they become ill again.
She was looking quite healthy on Friday, but she had/suffered a relapse over the weekend and was taken back into hospital. 周五的时候她看上去还很健康，但到了周末病情复发，又被送回了医院。