1) the soft growth between the back of the nose and the throat, sometimes making breathing difficult (adenoids)

2) the shell on the back of a tortoise etc (carapace)

3) to write one's name on the back of (a cheque) (endorse)

4) the tendon at the back of the knee; to destroy the power or efficiency of (a person, army etc) (hamstring)

5) the back of the neck (nape)

6) one of a pair of baskets placed across the back of a horse or donkey; one of a pair of bags on either side of the back of a bike or motorbike (pannier)

7) the space (with the muscles etc that enclose it) at the back of the mouth (pharynx)

8) something that reflects heat, light or sound, e.g. a piece of glass for reflecting light on the back of a bicycle (reflector)

9) a flat piece of wood or metal at the back of a plane, used for steering (rudder)

10) the back of the neck when used for grasping (scruff)