先后的英文：
early or late
priority
in succession
one after another

A policeman and then a paramedic tried to resuscitate her.
一名警察和一位护理人员先后试图救活她。

In order of precedence
按先后次序

All (names are arranged) in random order.
排名不分先后

Things should be taken up in order of priority.
办事应有个先后次序。

Events in chronological order,ie according to times,dates,etc
按时间先后排列的事件

He wrote the words in alphabetical order.
他按字母的先后把单词写下。

They addressed the Conference briefly or at length.
他们先后在会上作了或短或长的发言。

In the gymnastic contest, the two teams kept abreast with each other.
在这次体操比赛中,两队并驾齐驱,不分先后。

He was abreast of the other runners.
他与其他赛跑者不分先后。

5 consecutive lots or batches have been considered acceptable on original inspection.
初检时先后有5批货检验合格。

Early sow, early mow.
早动手，早收获。

Early ripe, early rotten.
早熟早烂(早慧早衰)。

Early to bed and early to rise, makes a man healthy.
早睡早起使人健康。

You are jolly late.
你来得很迟。

And then, in the late afternoon the sky will clear,
然后，下午晚些时候天空变晴，

Never too late to repent
过则勿惮改

Road building is a top priority.
筑路是最优先考虑的事。

Maintaining stability is of top priority.
稳定压倒一切。

It was a matter of balancing priorities.
这是一个权衡轻重缓急的问题。