of course 当然

Of course, I'm lucky enough. 当然，我够幸运。

on average 平均；通常

We work 10 hours a day on average. 我们平均每天工作10个小时。

on business 有事；出差

She's in Qingdao on business. 她出差到青岛去了。

on foot 步行；走路

Jenny goes to school on foot. 珍妮步行去上学。

on holiday 在休假

I'll fly to Paris on holiday for the whole week. 我要乘飞机去巴黎度假一周。

on one's side 在某人一边

Many of them are on his side. 他们中间许多人站在他的一边。

on the phone 在打电话

It's rude to shout on the phone. 在电话里大声嚷嚷是粗鲁的。

on the other hand 在另一方面

On the other hand, she is clever. 另一方面, 她很聪明。

on the/one's way(to) 在去……的路上

She passes my house on the way to school. 她上学的路上经过我家。

on time 准时

We will arrive at the meeting on time. 我们将准时到会。

on weekdays 在工作日

I'm busy on weekdays. 我工作日很忙。

once every four years 每四年一次

The Football World Cup is held once every four years. 足球世界杯四年举办一次。

once more/again 再次

Speak once more, please. 请再说一遍。

one after another 一个接一个；连续地

He ate three hotdogs one after another. 他一个接一个地吃了3个热狗。

out of 从……里出来；缺乏

She is out of danger. 她脱离了危险。

out of date 过时

My handbag is out of date this year. 我的手提包今年过时了。

over and over 再三；一次次

She kept on telling us the same story over and over. 她一遍又一遍地给我们讲同一个故事。