once

once, as soon as

• once he makes up his mind，he’ll never give it up.
  他一旦下定决心，就决不会放弃（本句不可用as soon as）。

• as soon as i get to beijing，i’ll write to you.
  我一到北京就写信给你。

副词 once:

1. on one occasion
   同义词：one time, in one case
2. as soon as
3. at a previous time;
   同义词：formerly, at one time, erstwhile, erst

1. Be pleasant to each other just this once.
   彼此要和睦些－－就只为这一次吧。
2. The film is at once humorous and moving.
   这部电影既幽默又动人。
3. Amanda is home from college once again.
   阿曼达又从学校回到家中。
4. All at once she lost her temper.
   她突然发起脾气来。
5. Once we lived in London.
   我们曾经住在伦敦。
6. Once is enough, never again.
   一次就够了，别再干了。
7. Once you begin, you must continue.
   一旦开始，你就得继续。
8. He stopped playing the piano at once.
   他立刻停止了弹钢琴。

once

adv.（副词）
One time only:
仅仅一次：
例句：
once a day.
一天一次

At one time in the past; formerly.
过去的某一时间；以前
At any time; ever:
从前；曾经：
例句：
Once known, his face is never forgotten.
曾经认识，他的面容让人永生难忘

By one degree of relationship:
关系相隔一代的：
例句：
my first cousin once removed.
我堂亲的孩子

n.（名词）
A single occurrence; one time:
发生一次；一次：
例句：
Once will have to do. You can go just this once.
必须去做一次，你只去这一回

conj.（连接词）
As soon as; if ever; when:
一…就；一旦；当…时：
例句：
Once he goes, we can clean up.
他一走，我们就能清理

adj.（形容词）
Having been formerly; former:
曾经的；以前的：
例句：
the once capital of the nation.
该国以前的首都

<习惯用语>at once
All at one time; simultaneously:
立刻；同时：
例句：
Everything happened at once. The view of the skyline is at once awesome, grand, and disappointing.
所有的事都一起发生了。天边立刻呈现出令人敬畏的、壮丽的和令人沮丧的景色

Immediately; instantly:
立即；马上：
例句：
Leave the room at once.
马上离开这个房间

来源：
Middle English ones
中古英语 ones
from on [one]
源自 on [一]
from Old English 3n * see oi-no-
源自 古英语 3n *参见 oi-no-