成绩退步很快的英文怎么说

在英语中，当成绩迅速下降时，可以用 "deteriorate rapidly" 来形容。

这个词组来自拉丁语 "deteriorare"，意思是 "使恶化、使变坏"。

下面是一些例句，希望对你有帮助：

His grades have deteriorated rapidly since he started missing class. (他因为缺课而成绩急剧下降。)
The economy has deteriorated rapidly due to the pandemic. (由于流行病，经济急剧恶化。)
The road conditions have deteriorated rapidly due to the heavy rain. (由于大雨，道路状况急剧恶化。)