sunshine vs sunniness

sunshine and sunniness both are nouns.

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

As nouns, sunshine and sunniness are synonyms defined as:

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

Other synonyms of sunshine include cheer, cheerfulness.

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