illness vs malady

illness and malady both are nouns.

Word	Noun	Adjective	Verb	Adverb
illness	Yes	No	No	No
malady	Yes	No	No	No

As nouns, illness and malady are synonyms defined as:

illness and malady: impairment of normal physiological function affecting part or all of an organism

Other synonyms of illness include sickness, unwellness.

illness (noun)	malady (noun)
impairment of normal physiological function affecting part or all of an organism	impairment of normal physiological function affecting part or all of an organism
	any unwholesome or desperate condition