apex vs extreme

apex and extreme both are nouns.

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

As nouns, extreme is a hypernym of apex; that is, extreme is a word with a broader meaning than apex:

Other hypernyms of apex include extreme point, extremum.

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

apex (adjective)	extreme (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