关于英语中once的用法

once
[wQns]
n.
adv.一次, 从前, 曾经
conj.
一旦

once
once
AHD:[w¾ns]
D.J.[wJns]
K.K.[wJns]
adv.（副词）
One time only:
仅仅一次：
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：
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：
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：
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：
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：
the once capital of the nation.
该国以前的首都

at once
All at one time; simultaneously:
立刻；同时：
Everything happened at once. The view of the skyline is at once awesome, grand, and