until:直到,I'll wait until you come. (我一直等到你来)not...until:直到...才,I won't leave until you come. (直到你来了我才离开)unless: =if...not 除非...(否则): I will go out for a walk unless it rains. (除非下雨,否则我要出去散步) = I will go out for a walk if it doesn't rain.(如果不下雨,我就出去散步)时态:通常为 主将从现 (主句用一般将来时,从句用一般现在时)