Is the mouth SUPERIOR to the nose? Is the stomach INFERIOR to the diaphragm?
The nose is superior to the mouth. The stomach is inferior to the diaphragm.
In anatomical terms, words like superior and inferior are road maps - they give some directions on a body.
For instance, the word superior refers to something above something else. Is the mouth above the nose? No. The nose is superior to the mouth.
The word inferior refers to something below something else. The stomach, for instance, lies below the diaphragm and so is inferior to it.
And so for the words superior and inferior, if a is superior to b, then b is inferior to a.
Here's a link to a comprehensive list of medical directional terms: