1.the posterior part of a human (or animal) body from the neck to the end of the spine;

his back was nicely tanned

2.the side that goes last or is not normally seen;

he wrote the date on the back of the photograph

3.the part of something that is furthest from the normal viewer;

he stood at the back of the stage

4.(football) a person who plays in the backfield

5.the series of vertebrae forming the axis of the skeleton and protecting the spinal cord;

the fall broke his back

6.the front and back covering of a book;

the book had a leather binding

7.the part of a garment that covers your back;

they pinned a `kick me' sign on his back

8.a support that you can lean against while sitting;

the back of the dental chair was adjustable

9.the position of a player on a football team who is stationed behind the line of scrimmage

10.related to or located at the back;

the back yard

11.located at or near the back of an animal;

back (or hind) legs

12.of an earlier date;

back issues of the magazine

13.in or to or toward a former location;

she went back to her parents' house

14.at or to or toward the back or rear;

he moved back

15.in or to or toward an original condition;

he went back to sleep

16.in or to or toward a past time;

set the clocks back an hour

17.in answer;

he wrote back three days later

18.in repayment or retaliation;

we paid back everything we had borrowed