简明英汉词典

 once upon a time
adv.
从前

现代英汉词典

 once
[wQns]
adv.

(1)

 一次，一回
I go to see a film once a week.
我每周看一场电影。
"Once a month, he has to collect money from his customers."
"每月一次,他得去向顾客收钱。"
Once a year a race is held for old cars.
每年举行一次旧式小汽车比赛。
"Attention please, I'll repeat the question once more."
请注意我把问题再重复一遍。

(2)

 从前； 曾经
She once knew him.
她以前认识他。
"Once, however, Big Ben failed to give the correct time."
"不过,有一次`大本钟'报错了时间。"
A good editor never once leaves a misprint uncorrected.
一个好编辑决不会放过一个印刷错误。
It once seemed inconceivable to everyone that men should travel to the moon.
"人们一度认为,人飞上月球似乎是不可想象的。"

习惯用语

 all at once
突然, 忽然

at once
马上，立刻；同时
Do it at once.
马上做。
Don't all speak at once!
大家别一块儿说话！

once (and) for all
最后一次
"Once and for all, we can't agree!"
"最后再说一遍,我们不能同意!"

once or twice
几次；一两次

once upon a time
从前
Once upon a time there was a poor old fisherman.
从前有一位贫穷的老渔夫。

词性变化

 once
conj.
一旦；一…就…
Once printed, this dictionary will be very popular!
一旦出版，这本词典将会非常畅销！
Once he arrives we can start.
他一到我们就可以动身。

once
n.
一次
Do it just this once.
只做这一次。
For once he was telling the truth.
他只有这一次说了实话。
"If one once loses self-confidence, he can never expect to be successful."
"一个人一旦失去了自信心,就甭想获得成功。"
Will once be enough?
一次就够了吗?

英汉航海大词典

 once upon a time
adv.从前

英汉化学大词典

 once upon a time
adv.从前

英汉经贸大词典

 once upon a time
n.从前

英汉计算机大词典

 once upon a time
adv.从前(古时候,很久以前)