rachitis vs avitaminosis

rachitis and avitaminosis both are nouns.

Word	Noun	Adjective	Verb	Adverb
rachitis	Yes	No	No	No
avitaminosis	Yes	No	No	No

As nouns, avitaminosis is a hypernym of rachitis; that is, avitaminosis is a word with a broader meaning than rachitis:

rachitis: childhood disease caused by deficiency of vitamin D and sunlight associated with impaired metabolism of calcium and phosphorus
avitaminosis: any of several diseases caused by deficiency of one or more vitamins

Other hypernyms of rachitis include hypovitaminosis.

rachitis (noun)	avitaminosis (noun)
childhood disease caused by deficiency of vitamin D and sunlight associated with impaired metabolism of calcium and phosphorus	any of several diseases caused by deficiency of one or more vitamins
inflammation of the vertebral column