请问.. "once in a ... " 是不是固定短语常常看到once in a life time once in a summer之类的..是什麼意思呢谢谢.

once in a while once.in.a. once in a 请问 once in blue moon 请问.. once in a ... 是不是固定短语常常看到once in a life time once in a summer之类的..是什麼意思呢谢谢. Once In A Lifetime是什么意思 once in a life time Once In A Lifetime 歌词 once-in-a-lifetime是什么意思 Once In A While 歌词 once in a blue room 请问：at once ,in a moment ,in a hearbeat ,in a snap,on the spot 有什么区别吗? What happens twice in every moment,once in every minute and never in a thousand years?请问这句话是什么意思? keep a diary once in a while Once In A Lifetime Love 歌词 Youare my once in a life time Once in love for a whole time. once in a while ?什么意思?