failure vs nonpayment

failure and nonpayment both are nouns.

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

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

failure (noun)	nonpayment (noun)
an act that fails	the deliberate act of failing to pay money
an unexpected omission	loss resulting from failure of a debt to be paid
an event that does not accomplish its intended purpose	act of failing to meet a financial obligation
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