[chú fēi]
（表示唯一的条件） only if; only when
Only when a reservoir is built here can we solve our irrigation problem.
除非在这里修个水库， 才能解决灌溉问题。
If you don't want people to know, you'd better not do it.
若要人不知，除非己莫为。
not otherwise rated
除非另有费率
not otherwise provided; not elsewhere specified
除非另有规定
not otherwise enumerated
除非另有列举
unless commenced earlier
除非提早开始装卸
Don't come unless I ring you up.
除非我打电话给你， 否则你不要来。
He'll certainly come unless he is ill.
他不会不来，除非他病了。