used to convey that the second event mentioned happens immediately after the first
一…就…
she had no sooner spoken than the telephone rang.
她刚一说话，电话就响了。
before much time has gone by
越早越好
I would be grateful if you would come to your senses sooner rather than later.
你要是能早点恢复理智我就谢天谢地了。
As soon as
一…就…
No sooner was the frost off the ground than the work began.
地上的霜一消散，人们就开始工作了
At some time; eventually
迟早；有朝一日
Sooner or later you will have to face the facts.
你迟早将面对事实