apex of the sun's way vs welkin

apex of the sun's way and welkin both are nouns.

Word	Noun	Adjective	Verb	Adverb
apex of the sun's way	Yes	No	No	No
welkin	Yes	No	No	No

apex of the sun's way (noun)	welkin (noun)
the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars	the apparent surface of the imaginary sphere on which celestial bodies appear to be projected