副詞adv.
1.一次,一回
I see them once every two months.
我每兩個月與他們見一次面。
2.昔日,曾經
He once knew her, but they are no longer friends.
他以前認識她,但他們已經不是朋友了。
名詞n.
1.一次,一回
Once is enough.
一次就夠了。
連線詞conj.
1.一旦,一經...便
Once you get into a bad habit, you'll find it hard to get out of it.
一旦染上壞習慣,想改掉就難了。