Refers to the back of a person or animal, from shoulders to waist.
彼は背中を壁にもたれかけた。
He leaned his back against the wall.
猫の背中をなでる。
I stroke the cat's back.
I walked while carrying my child on my back.
My back hurts because I was sitting for a long time.
My friend patted me on the back to encourage me.
The child rode on the elephant's back.