认真的单词的英文是"diligent".
这个单词来源于拉丁文"diligentia"，原意是"carefulness"或"attentiveness"。
例句：
She is a diligent student who always does her homework on time. 她是一个认真的学生，总是按时完成作业。
The teacher praised him for his diligence in studying for the test. 老师赞扬他为了考试而勤奋学习。
希望这些信息对您有帮助。