once

adv.

一次，一趟；一倍；曾经；一旦

conj.

一旦…就…；一经；

n.

一次，一回；

1. Once or twice she looked over her shoulder at me.
   有一两次她回头看看我。
2. She had not once spoken to him all the evening.
   整整一晚上,她都没有跟他讲过一次话。
3. I see them about once a fortnight.
   我大约两星期见他们一次。
4. Once we lived in London.
   我们曾经住在伦敦。

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