“down”与“downstairs”有何区别?

“down”与“downstairs”有何区别? fall off 与fall down有何区别? burn down与burn up有何区别 请问come down 和go down 有何区别? my computer broke与my computer broke down有何区别? lie down和lie on有何区别 Down payment 和 advance payment 有何区别? turn down 与 keep down 有什么区别? 与对不起有何区别? 请问go along 、go straight 、 go straight down 、go down有何区别? 唯心主义与唯物主义有何区别,有何特点? down 与have been down的区别