Is the noun "heaven" used as both singular and plural?
Thank you in advance.
No. Why should the plural not be "heavens" as for most English plurals?
"The pilot was flying up in the heavens.", "The rain fell from the heavens."
'Heaven", the place that good people go when they die in certain mythologies is properly called Heaven, since it's the name of a place. "The Heavens of Christianity and Islam are different" - although the Islam 'heaven' is usually translated as Paradise. Even if the capital wasn't used, it would still be 'heavens'.
Have you heard 'heaven' used as a plural?