如果你加热冰,冰就会融化I don't know whether the earth arounds the sun.我不知道地球是否绕着太阳转I don't understand whether the moon reflects the sunlight.我不了解是否月亮是反射太阳的光The difference between IF and WHETHER Whether 只适用于名词性从句,可以引导主语从句,且可以直接接不定式(to do )。但不用于否定结构(选择疑问句除外)If只用于及物动词引导的名词性从句,且不能引导主语从句和不定式。但是可以引导否定结构I don't care if he doesn't come.当与Or Not连用的时候,只能用Whether