What is the difference between those two? Are they synonyms?
Abdomen - The part of the body of a vertebrate containing the digestive organs; the belly. In humans and other mammals, it is bounded by the diaphragm and the pelvis.
Belly - The front part of the human trunk below the ribs, containing the stomach and bowels.
Stomach - The internal organ in which the major part of the digestion of food occurs, being (in humans and many mammals) a pear-shaped enlargement of the alimentary canal linking the esophagus to the small intestine.
What words should I use for each of them? Thank you.
And which one is more natural in daily usage to be used in sentences such as " I have stomach ache" or "My abs is six-pack"?
I asked this question because in Bahasa Indonesia (my language), there is only one word to describe all of them, that is "Perut". So, six pack abs translates to "Perut six pack" as stomach ache to "Sakit perut". Just like Japanese, there's no word that describe "Jaw", chin and jaw in Japanese translates to the same word あご.