*[wʌns]
ad. 一次, 曾经, 一旦
conj. 一旦, 一经
n. 一次
a. 从前的
相关词组:
once or twice
not once
all at once
at once
at once…and…
more than once
once more
once and again
once and away
once and for all
once in a way
once in a while
once too often
just for once
once upon a time
once a week