annuity vs regular payment

annuity and regular payment both are nouns.

Word	Noun	Adjective	Verb	Adverb
annuity	Yes	No	No	No
regular payment	Yes	No	No	No

As nouns, regular payment is a hypernym of annuity; that is, regular payment is a word with a broader meaning than annuity:

annuity: income from capital investment paid in a series of regular payments
regular payment: a payment made at regular times

annuity (noun)	regular payment (noun)
income from capital investment paid in a series of regular payments	a payment made at regular times