pollyannaish vs upbeat

pollyannaish is not a noun while upbeat is a noun.

Word	Noun	Adjective	Verb	Adverb
pollyannaish	No	Yes	No	No
upbeat	Yes	Yes	No	No

As adjectives, pollyannaish and upbeat are synonyms defined as:

Other synonyms of pollyannaish include cheerful.

pollyannaish (noun)	upbeat (noun)
	an unaccented beat (especially the last beat of a measure)
	a contented state of being happy and healthy and prosperous

pollyannaish (adjective)	upbeat (adjective)
pleasantly (even unrealistically) optimistic	pleasantly (even unrealistically) optimistic