[yī cì]

once a week
一周一次

more than once
不止一次

once again
再一次

try once again
再試一次

Will once be enough?
一次就夠了嗎?

The increasing distance between thunderclaps meant the storm was moving away.
雷聲隔得一次比一次久， 這意味著暴風雨正在過去。

I have been there once.
我到過那兒一次。

I've met her only once.
我只見過他一次。