Once delivered to the end-point manager, the sender can be assured that the message will be delivered or a definite event (time out) will be raised.

一旦传递给了端点管理器，发送方可以确信消息将被传递或是将会引发一个明确的事件(超时)。

youdao

So that examining in time the relation of commands to events, we find that the command can never in any case be the cause of the event, but that a certain definite dependence exists between them.

因此，考查命令与事件在时间上的关系时，我们就发现，命令无论如何不是事件的原因，而两者之间不过存在着一定的关系罢了。

youdao

It means the host needs a definite head count for the planned event, and needs it by the date specified on the invitation.

FORBES: Importance of the RSVP