renal failure vs nephrosis

renal failure and nephrosis both are nouns.

Word	Noun	Adjective	Verb	Adverb
renal failure	Yes	No	No	No
nephrosis	Yes	No	No	No

As nouns, nephrosis is a hypernym of renal failure; that is, nephrosis is a word with a broader meaning than renal failure:

renal failure: inability of the kidneys to excrete wastes and to help maintain the electrolyte balance
nephrosis: a disease affecting the kidneys

Other hypernyms of renal failure include failure, kidney disease, nephropathy, renal disorder.

renal failure (noun)	nephrosis (noun)
inability of the kidneys to excrete wastes and to help maintain the electrolyte balance	a disease affecting the kidneys
	a syndrome characterized by edema and large amounts of protein in the urine and usually increased blood cholesterol; usually associated with glomerulonephritis or with a complication of various systemic diseases