留
Meaning
- to leave (a message etc)
- to retain
- to stay
Example sentence
留点儿神！
Be more aware!
The character 留
留 is leaving something behind rather than taking it: 留下 to leave it, 留言 to leave a message, 保留 to hold back. 留学 is staying abroad to study, and 留学生 is the one who does.