once and for all

1. 永遠地；最後一次
   John's back home once and for all.

   約翰回到家，再也不走了。

once in a while

1. 有時
   He went to see them once in a while.

   他有時去探望他們。

once more/again

1. 再一次
   John's back home once more.

   約翰又回家了。

once or twice

1. 幾次
   I've been there once or twice.

   我到過那裡幾次。

once too often

1. 又一次
   He exceeded the speed limit once too often.

   他又超速行駛了。

all at once

1. 突然
   He left all at once.

   他突然離開了。

at once

1. 馬上；立刻
   Do it at once!

   馬上就做！

for once

1. 僅這一次
   For once he was telling the truth.

   他就這一次說了真話。

once in a way

1. 有時；偶爾

• all at once
  
  1. suddenly.
  2. all at the same time.
• at once
  
  1. immediately.
  2. simultaneously.
• for once (or this once)
  on this occasion only.
• once again (or more)
  one more time.
• once and for all (or once for all)
  now and for the last time; finally.
• once (or every once) in a while
  occasionally.
• once or twice
  a few times.
• once upon a time
  at some time in the past.