upon

US /əˈpɑːn/
UK /əˈpɑːn/
"upon" picture
1.

在...上, 基于

more formal term for on, especially in abstract senses

:
The decision was based upon careful consideration.
该决定是基于仔细考虑而作出的。
He placed the book upon the table.
他把书放桌子
2.

一...就, 在...之后

indicating a time immediately or very soon after something

:
Upon arrival, please report to the front desk.
抵达后,请到前台报到。
He started crying upon hearing the news.
一听到这个消息就哭了。