Meaning

noun the highest point (of something)

noun the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars

originEtymology tree Proto-Indo-European *h₂ep-der. Proto-Italic *apeks Latin apexbor. English apex Borrowed from Latin apex (“point, tip, summit”).

Etymology from Wiktionary, CC BY-SA 3.0