down payment vs payment

down payment and payment both are nouns.

Word	Noun	Adjective	Verb	Adverb
down payment	Yes	No	No	No
payment	Yes	No	No	No

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

down payment: a partial payment made at the time of purchase; the balance to be paid later
payment: a sum of money paid or a claim discharged

down payment (noun)	payment (noun)
a partial payment made at the time of purchase; the balance to be paid later	the act of paying money
	an act of requiting; returning in kind
	a sum of money paid or a claim discharged