extreme vs apex

extreme and apex both are nouns.

Word	Noun	Adjective	Verb	Adverb
extreme	Yes	Yes	No	No
apex	Yes	No	No	No

As nouns, apex is a hyponym of extreme; that is, apex is a word with a more specific, narrower meaning than extreme:

Other hyponyms of extreme include acme, peak, vertex.

extreme (noun)	apex (noun)
the furthest or highest degree of something	the highest point (of something)
the point located farthest from the middle of something	the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars

extreme (adjective)	apex (adjective)
most distant in any direction
far beyond a norm in quantity or amount or degree; to an utmost degree
of the greatest possible degree or extent or intensity
beyond a norm in views or actions