apex

Etymology

Borrowed from Latin apex (“point, tip, summit”).

noun

1. The highest or the greatest part of something, especially forming a point.
   1. (geometry) The highest point in a plane or solid figure, relative to a base line or plane.
   2. (chiefly anatomy) The pointed fine end of something.
      1. The lowest part of the human heart.
         B.P. 118/68. Grade I diastolic murmur best heard over apex. Patient well and had no complaints referable to heart. Origin of the diastolic murmur is open to conjecture. 1951 March, J. H. Lehmann, A. D. Johnson, W. C. Bridges, J. Michel, D. M. Green, “Cardiac Catheterization—A Diagnostic Aid in Congenital Heart Disease”, in Northwest Medicine, volume 50, number 3, Portland, Ore.: Northwest Medical Publishing Association, page 175
      2. The deepest part of a tooth's root.
   3. (botany) The end of a leaf, petal or similar organ opposed to the end where it is attached to its support.
   4. (botany) The growing point of a shoot.
   5. (astronomy) The point on the celestial sphere toward which the Sun appears to move relative to nearby stars.
   6. (physics) The lowest point on a pendant drop of a liquid.
   7. (mining, US) The end or edge of a vein nearest the surface.
   8. (typography):
      1. A diacritic in Classical Latin that resembles and gave rise to the acute.
      2. A diacritic in Middle Vietnamese that indicates /ŋ͡m/.
      3. A sharp upward point formed by two strokes that meet at an acute angle, as in "W", uppercase "A", and closed-top "4", or by a tapered stroke, as in lowercase "t".
         Coordinate term: vertex
2. (figurative) The moment of greatest success, expansion, etc.
   the apex of civilization
   It would be an intense disgust. The absolute apex of teen angst. 2002, Jeffrey Rowland, “Day 2 (The Slagathors)”, in Wigu Adventures, page 58
   The pattern has repeated itself more times than you can fathom. Organic civilizations rise, evolve, advance. And at the apex of their glory, they are extinguished. 2008, BioWare, Mass Effect (Science Fiction), Redwood City: Electronic Arts, →OCLC, PC, scene: Virmire
3. (attributive, ecology) The top of the food chain.
4. A conical priest cap.