The noun "apex" refers to the highest or greatest part of something, such as the highest point in a plane or solid figure, the pointed fine end of something, the end of a leaf or petal opposite to where it is attached, the growing point of a shoot, the point on the celestial sphere toward which the sun appears to move, the lowest point on a pendant drop of a liquid, the end or edge of a vein nearest the surface in mining, and a diacritic or sharp upward point in typography.

(figurative) The moment of greatest success, expansion, etc.

(attributive, ecology) The top of the food chain.

A conical priest cap.