failure vs flunk

failure and flunk both are nouns.

Word	Noun	Adjective	Verb	Adverb
failure	Yes	No	No	No
flunk	Yes	No	Yes	No

As nouns, flunk is a hyponym of failure; that is, flunk is a word with a more specific, narrower meaning than failure:

failure (noun)	flunk (noun)
an act that fails	failure to reach a minimum required performance
an unexpected omission
an event that does not accomplish its intended purpose
a person with a record of failing; someone who loses consistently
lack of success
loss of ability to function normally
inability to discharge all your debts as they come due

failure (verb)	flunk (verb)
	fail to get a passing grade