Belly: That part of the body that contains all of the structures between the chest and the pelvis. Also called the abdomen.
The belly (or abdomen) is separated anatomically from the chest by the diaphragm, the powerful muscle spanning the body cavity below the lungs.
The belly contains a host of organs including the stomach, small intestine, colon, rectum, liver, spleen, pancreas, kidneys, appendix, gallbladder, and bladder.
The word "abdomen" has a curious story behind it. It comes from the Latin "abdodere", to hide. The idea was that whatever was eaten was hidden in the abdomen.