move backward；make sth backward
She backed against the wall, terrified.
You'll have to back the car up into the garage.
We were sitting in the back row,so it is hard to see the singer clearly.
It doesn't matter. It was a back number anyway.
a back pay/rent/taxes
He was unemployed and owed 2 months'back rent.
The boss must provide back rent with workers.
at the back of
Could you feel anything at the back of it?
at the back of mind
I have an idea at the back of mind that I met him somewhere.
be one's back
He must be his back because he has no choice.
turn one's back on
I turned to him for help ,but he turned his back on me.
She turned her back on what she insisted
behind one's back
We should not speak ill of a man behind his back, which is impolite.
take a back seat
The senior took a back seat and made room for the young and new ideas.
back and forth
The wind moved the twigs gently back and forth.
there and back
Can I go there and back in one day？
break one's back（全力以赴）
bring back to health(恢复健康)
hand back (物归原主）
sit back (袖手旁观）