Apex (noun)

1. The highest point of something, especially a mountain or roof.
2. The highest or culminating point, especially of achievement or development.

Origin:

Late 16th century: from latin apex "summit", originally "a point", from apere "be sharp".

Examples:

1. Mount Everest is the apex of the Himalayan mountain range.
2. The apex of his career was when he won the Nobel Prize for Literature.
3. The apex of the roof was just high enough for a tall person to stand up straight.
4. The company's success was at its apex during the early 2000s.
5. The apex of a triangle is the point at the top of the triangle, opposite the base.