I will wait for you on the condition that you promise to come.
我会等你但条件是你答应过来。
We all believe you on the condition that you tell us the truth.
我们都会相信你，条件是你告诉我们真相。
I can lend you the MP3 on the condition that you return it on time.
我可以把MP3借给你，但条件是你必须限期归还。