heliotherapy vs insolation

heliotherapy and insolation both are nouns.

Word	Noun	Adjective	Verb	Adverb
heliotherapy	Yes	No	No	No
insolation	Yes	No	No	No

As nouns, heliotherapy and insolation are synonyms defined as:

heliotherapy (noun)	insolation (noun)
therapeutic exposure to sunlight	therapeutic exposure to sunlight
	incident solar radiation
	sudden prostration due to exposure to the sun or excessive heat