/wʌns; wʌns/
adv
1 on one occasion only; (for) one time 仅仅一次; （作为）一次
*I've only been there once. 我只去过那里一次.
* He cleans the car once a week, a fortnight, etc, ie every week, every fortnight, etc. 他一星期、半月等擦一次车.
* She goes to see her parents in Wales once every six months. 她每半年回威尔士看父母一次.
2 (a) at some (indefinite) time in the past 一度; 曾经
*I once met your mother. 我曾经见过你的母亲.
* He once lived in Zambia. 他一度住在赞比亚.
(b) formerly 从前; 过去; 往日
*This book was once famous, but nobody reads it today. 这本书从前很出名, 现在没人看了.
3 (in negative sentences or questions 用于否定句或疑问句) ever; at all; even for one time 根本; 即使一次
*He never once/He didn't once offer to help. 他从未[根本没]主动提出帮忙.
* Did she once show any sympathy? 她表示过同情吗?
4 (idm 习语) ,all at `once suddenly 突然
*All at once the door opened. 门突然打开了.
* All at once she lost her temper. 她突然大发雷霆. at `once
(a) immediately; without delay 立刻; 马上; 立即
*Come here at once! 立刻到这里来!
* I'm leaving for Rome almost at once. 我马上就要去罗马.
(b) at the same time 同时
*Don't all speak at once! 不要大家一齐说!
* I can't do two things at once. 我无法同时做两件事.
* The film is at once humorous and moving. 这部电影既幽默又动人. (just) for `once; just this `once on this occasion only, as an exception 仅此一次; 作为例外
*Just for once he arrived on time. 只有这次他是按时到了.
* Be pleasant to each other just this once. 彼此要和睦些--就只为这一次吧. get/give sb/sth the `once-over (infml 口) get/give sb/sth a quick inspection or examination 粗略检查或察看某人[某事物]
*Before buying the car he gave it the once-over. 他买那辆车前曾草草看了一下.
* She felt his parents were giving her the once-over. 她感到他父母打量着她. once `again; once `more one more time as before 再一次
*I'll tell you how to do it once again. 我再告诉你一次怎么做.
* Amanda is home from college once again. 阿曼达又从学校回到家中. ,once and for `all now and for the last (and only) time 这一次且为最後一次
*I'm warning you once and for all. 我给你最後一次警告.
* He's travelled a lot but he's now come back to Britain once and for all. 他游历了许多地方, 现在落叶归根又回到了英国. ,once `bitten, ,twice `shy (saying 谚) after an unpleasant experience one is careful to avoid sth similar 一次被咬, 下次胆小; 一次上当, 下次小心
*She certainly won't marry again once bitten, twice shy. 她肯定不再结婚了--所谓一朝被蛇咬, 十年怕井绳. ,once in a blue `moon (infml 口) very rarely or never 极少; 从不
*I see her once in a blue moon. 我难得看到她. (every) ,once in a `while occasionally 偶尔; 间或
*Once in a while we go to a restaurant but usually we eat at home. 我们偶尔下馆子--但一般都在家吃. once `more
(a) one more time; again 再一次; 又一次
*Let's sing it once more. 咱们再唱一次吧.
(b) = once again. ,once or `twice a few times 一两次
*I don't know the place well, I've only been there once or twice. 我对那地方不大熟悉, 只去过一两次. ,once too `often once more than is sensible or safe 这一次却未能幸免
*He had driven home drunk once too often -- this time he got stopped by the police. 他多次醉酒开车回家, 上得山多终遇虎--这回让警察截住了. ,once upon a `time (used as the beginning of a fairy-tale 用于童话开头) at some indefinite time in the past 从前; 古时候
*Once upon a time there was a beautiful princess... 从前有个美丽的公主.... you're only young once => only2.

conj as soon as; when 一旦; 一...就...
*Once you understand this rule, you'll have no further difficulty. 一旦明白了这条规则, 就再也没有困难了.
* How would we cope once the money had gone? 钱一用完, 我们怎么办?