1.be uesd in 指用于什么情况下,用于什么场合.2.be used for doing sth. 用来干……的例如：The pencil is used for drawing and writing.铅笔可以用来画画和写字.3.be used as sth.被作为……用
例句：This book can be used as a text book. 这本书可以被当作课本用.
The big table can be used as a bed. 这个大桌子可以当床用.
4.be used by sb 被某人使用 例句：The machine is used by workers.这台机器是工人们使用的.