firmament vs apex of the sun's way

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

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

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