welkin vs empyrean

welkin and empyrean both are nouns.

Word	Noun	Adjective	Verb	Adverb
welkin	Yes	No	No	No
empyrean	Yes	Yes	No	No

As nouns, welkin and empyrean are synonyms defined as:

welkin and empyrean: the apparent surface of the imaginary sphere on which celestial bodies appear to be projected

Other synonyms of welkin include celestial sphere, firmament, heavens, sphere, vault of heaven.

welkin (noun)	empyrean (noun)
the apparent surface of the imaginary sphere on which celestial bodies appear to be projected	the apparent surface of the imaginary sphere on which celestial bodies appear to be projected

welkin (adjective)	empyrean (adjective)
	of or relating to the sky or heavens
	inspiring awe