背部

例句：

1. 1. He sat on the back of the couch and watched TV.
   他坐在沙发的背部看电视。
2. 2. The doctor advised him to lie flat on his back.
   医生建议他平躺。
3. 3. She lifted her back up after she fell asleep.
   她睡着后，她把背挺起来。