amortisation vs defrayal

amortisation and defrayal both are nouns.

Word	Noun	Adjective	Verb	Adverb
amortisation	Yes	No	No	No
defrayal	Yes	No	No	No

As nouns, defrayal is a hypernym of amortisation; that is, defrayal is a word with a broader meaning than amortisation:

amortisation: payment of an obligation in a series of installments or transfers
defrayal: the act of paying money

Other hypernyms of amortisation include defrayment, payment.

amortisation (noun)	defrayal (noun)
payment of an obligation in a series of installments or transfers	the act of paying money
the reduction of the value of an asset by prorating its cost over a period of years