mediastinum vs bodily cavity

mediastinum and bodily cavity both are nouns.

Word	Noun	Adjective	Verb	Adverb
mediastinum	Yes	No	No	No
bodily cavity	Yes	No	No	No

As nouns, bodily cavity is a hypernym of mediastinum; that is, bodily cavity is a word with a broader meaning than mediastinum:

mediastinum: the part of the thoracic cavity between the lungs that contains the heart and aorta and esophagus and trachea and thymus
bodily cavity: (anatomy) a natural hollow or sinus within the body

Other hypernyms of mediastinum include cavity, cavum.

mediastinum (noun)	bodily cavity (noun)
the part of the thoracic cavity between the lungs that contains the heart and aorta and esophagus and trachea and thymus	(anatomy) a natural hollow or sinus within the body