parlay vs bet on

parlay is a noun but bet on is not a noun.

Word	Noun	Adjective	Verb	Adverb
parlay	Yes	No	Yes	No
bet on	No	No	Yes	No

As verbs, bet on is a hypernym of parlay; that is, bet on is a word with a broader meaning than parlay:

Other hypernyms of parlay include back, gage, game, punt, stake.

parlay (noun)	bet on (noun)
a series of wagers in which the winnings from one wager are used as a stake for the subsequent wagers

parlay (verb)	bet on (verb)
stake winnings from one bet on a subsequent wager	place a bet on