again and again,over and again,over and over again, time and again,over and over

这几个词均表示重复或反复。
again and again侧重行为、经历、活动的多次出现且未必在同一个时间。

over and again一指声音断断续续或不时地传出，一指言语的多次重复，反复或再三地三令五申，有关心、希望、激动、绝望等意味，是有意义的重复。

time and again显示一种牢骚与不耐烦。

over and over是亲切、温暖的念叨，常常是自言自语。

over and over again一方面具有over and over的意思，且比它更强调，一方面又可表示机械性或无意义的重复。

例句：
1、He reviewed the texts again and again before exam.
   考试之前，他反复复习课文。
2、Over and again we heard the cry from the hut on the hill.
   不时地听到山上小屋里传来的叫声。
3、The performance was warmly applauded and cheered over and again by the audience.
   表演受到观众们一次次热烈的鼓掌和喝彩。
4、He was made to spell the same word over and over again.
   他被要求不断重拼同一个单词。
5、I told you time and again not to believe in him.
   我多少次告诉你不要相信他。
6、Over and over he whispered the name of his lover.
   他不断轻轻唤着他情人的名字。