sunniness vs sunshine

sunniness and sunshine both are nouns.

Word	Noun	Adjective	Verb	Adverb
sunniness	Yes	No	No	No
sunshine	Yes	No	No	No

As nouns, sunniness and sunshine are synonyms defined as:

sunniness and sunshine: the quality of being cheerful and dispelling gloom

Other synonyms of sunniness include cheer, cheerfulness.

sunniness (noun)	sunshine (noun)
lightness created by sunlight	the quality of being cheerful and dispelling gloom
the quality of being cheerful and dispelling gloom	the rays of the sun
	moderate weather; suitable for outdoor activities