vertex vs apex

vertex and apex both are nouns.

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

As nouns, vertex and apex are synonyms defined as:

Other synonyms of vertex include acme, peak.

vertex (noun)	apex (noun)
the point of intersection of lines or the point opposite the base of a figure	the highest point (of something)
the highest point (of something)	the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars