Definition
An expression used to show agreement to an offer or challenge.
（表示同意）好；行；一言为定。
"I challenge you to a round of golf next week!" "You're on!"
「我下星期要跟你比一场高尔夫！」「一言为定！」
"If I can finish this report in thirty minutes, can I leave work early?" "You're on!"
「如果我能三十分钟内完成这份报告，我可以提早下班吗？」「好！」
"Let's have a race to see who can run three laps around the field first." "You're on!"
「我们来比赛，看谁能先绕着场地跑三圈。」「一言为定！」