副词
1. I see them once every two months.
我每两个月与他们见一次面。
2. If the facts once become known, he will be punished.
事实一旦公开，他就要受到惩罚。
3. once什么意思
3. He once knew her, but they are no longer friends.
他以前认识她，但他们已经不是朋友了。
名词
1. once
1. Once is enough for me.
对我来说一次就够了。
连词
1. Once you begin you must continue.
你一旦开始，便不可停下来。