once/ w^ns /

1.adverb
(one time only) 一次

2.adverb
(at one time) 曾经

Texas was once ruled by Mexico.
德克萨斯州曾经受墨西哥管辖。
3.adverb
(on one occasion) 有一次

I went to Portugal once.
我去过一次葡萄牙。
4.conjunction
(as soon as) 一旦

at once
立刻
5.conjunction
(simultaneously) 同时

once a {or} every month
每月一次
once more {or} again
再一次
once and for all
一劳永逸地
once upon a time
很久以前
6.conjunction
(in the past) 从前

once in a while
偶尔
all at once
突然
for once
就这一次
just this once
 [inf] 就这一次
once or twice
一两次
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