The stomach — the place where food goes and where you feel hungry, full, or sick. It is a gentle, warm word, first learned by very small children, and it stays useful all your life for soft or slightly private talk about the body. Parents and nurses use it with children ('Does your tummy hurt?'), adults use it with each other in a light way ('my tummy's rumbling'), and it is the normal polite word for the front of the body between chest and hips, especially the soft part — 'a flat tummy', 'tummy fat'. That last use is interesting: in fitness and beauty writing, English chooses 'tummy' over 'stomach' or 'belly' on purpose, because 'tummy' sounds kind and not shaming. It is common in both Britain and America, and unlike 'tum' it does not sound old-fashioned. Note it means the whole soft front area in ordinary use, not only the stomach organ that doctors mean.