failure vs default

failure and default both are nouns.

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

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

failure (noun)	default (noun)
an act that fails	loss due to not showing up
an unexpected omission	an option that is selected automatically unless an alternative is specified
an event that does not accomplish its intended purpose	loss resulting from failure of a debt to be paid
a person with a record of failing; someone who loses consistently	act of failing to meet a financial obligation
lack of success
loss of ability to function normally
inability to discharge all your debts as they come due

failure (verb)	default (verb)
	fail to pay up