【词组解析】 

1.once again 再一次

（1）Violence once again irrupted into their peaceful lives.

       他们平静的生活中再度爆发了暴力冲突。

（2）The terrible specter of civil war hung over the country once again.

       内战的可怕阴影再一次笼罩这个国家。

2. once in a while 偶尔

（1）He went to see them once in a while.

       他偶尔去探望他们。

（2）You can hear people fall about laughing once in a while during the show.

       演出期间经常传来观众的大笑。

3. once more 再一次

（1）Sad to say, she wouldn't allow me to try once more.

       很不幸，她不让我再试一次。

（2）Let's act out the story of the three bears once more.

       让我们再次表演一下三只熊的故事。

4. once upon a time 从前

（1） Once upon a time there was a giant with two heads.

        从前有个两头巨人。

（2）Once upon a time in a faraway land there lived a princess in a big castle.

        从前，在很远的地方，有一位美丽的公主住在一座很大的城堡里。

5. one another 相互

（1）We all try and help one another.

       我们都尽力互相帮助。

（2）They smiled uncertainly at one another.

       他们犹豫地相视而笑。

【练习】

英译中：

（1）Let me remind you once again so that you won't forget.

（2）He comes to our room for a chat every once in a while.

（3）I shall be glad to see the old home once more.

（4）Once upon a time, there lived an old man who had two beautiful daughters.

（5）The two lines of bones are set perpendicular to one another.