prophylactic vs cautionary

prophylactic is a noun but cautionary is not a noun.

Word	Noun	Adjective	Verb	Adverb
prophylactic	Yes	Yes	No	No
cautionary	No	Yes	No	No

As adjectives, prophylactic and cautionary are synonyms defined as:

prophylactic (noun)	cautionary (noun)
contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse
remedy that prevents or slows the course of an illness or disease

prophylactic (adjective)	cautionary (adjective)
preventing or contributing to the prevention of disease	serving to warn
warding off	warding off
capable of preventing conception or impregnation