she is back是她回来了
back做名词名词 n.
1.背脊,背部[C]
Someone patted me on the back.
有人在我背上轻轻地拍了一下.
2.后部[the S][(+of)]
Grandpa and grandma sat in the back of the car.
爷爷和奶奶坐在汽车后排的座位上.
3.后面,背面[the S][(+of)]
4.椅背[the S] [(+of)]
5.(书报等的)末尾[the S][(+of)]
There is an appendix at the back of the book.
该书末尾处有一附录.
6.(足球等的)后卫;后卫球员[C][U]
she is a back是 她是后卫球员 back应是后卫的意思
再问： 请问she is back中,is和back都是动词，为什么能连用？
再答： she is back 是主系表结构。在这个句子中,把back看作一个形容词．理解为”回来的，回程的”意思。此时，she是主语,is是be动词作系动词，back为形容词作表语。
