once是什么词性

once 有两种词性

conj.一旦;一…就;当…时候

adv.曾经;曾;一次;仅一次;(用于否定句、疑问句和if后)曾，根本

例句

We didn\'t know how we would cope once the money had gone.

一旦钱花光了，我们就不知道该怎么办了。

She fell in with my idea at once.

她立刻同意了我的主意。

If you can only exercise once a week, that\'s better than nothing.

即便是一个星期锻炼一次，也比完全不锻炼好。

It was once thought that the sun travelled around the earth.

人们曾经认为太阳绕着地球转。

Let me hear it just once more.

让我再听一遍。