how soon 与how long的区别

how long,how soon和how often都含有how,并且都和“多长时间、多久”有关,但它们的用法不相同.how long意为“多久、多长时间”,主要是对一段时间进行提问,答语通常是（for）three days/weeks/months等时间段,它可用于各种时态.
How long do you stay in Beijing every year?每年你在北京住多久?How long have they lived here?他们住在这里有多久了?—How long were you not at school last year?去年你多久没上学?—About two weeks.约两周.
how soon意为“还要多久”,是对从某个基本时间到将来某动作结束或某动作发生这段时间提问,常用在一般将来时态的句子中,其答语通常是“in + 一段时间”.—How soon can you finish the work?还要多久你能完成这项工作?—In half an hour.半小时后.