【词组解析】
1. on purpose 故意地
（1）I don't think he stepped on your toes on purpose.
我想他不是有意伤害你的感情。
（2）She sometimes does things on purpose just to annoy me.
她有时存心做些事来使我生气。
2. on sale 出售,廉价出售
（1）There are some nice apples on sale in that shop.
那家商店有些很好的苹果出售。
（2）This ten-dollar hat is now on sale for five.
十美元一顶的帽子现在减价卖五美元。
3. on schedule 按时间表,准时
（1）Barring strong headwinds, the plane will arrive on schedule.
如果不是猛烈的顶头风，飞机会准点到达的。
（2）I have accomplished the task on schedule.
我按时完成了任务。
4. on second thoughts 经重新考虑
（1）On second thoughts he changed his mind.
进一步考虑后，他改变了主意。
（2）On second thoughts I took it with me.
经过再三考虑我带去了它。
5. on the contrary 正相反
（1）You think you are clever; on the contrary, I assure that you are very foolish.
你自以为很聪明，相反地，我确信你很傻。
（2）On the contrary, he passionately affirmed the goal of unity for Europe.
相反，他热情地肯定欧洲统一的目标。