noun (n)

• the highest point (of something)(noun.location)

  Synonym:
  acme, peak, vertex
  

  source: wordnet30
• the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars(noun.location)

  Antonym:
  antapex
  

  source: wordnet30
• The tip, top, point, or angular summit of anything; as, the apex of a mountain, spire, or cone; the apex, or tip, of a leaf.(noun)

  source: webster1913