a ‧ pex /ˈeɪpeks/ BrE AmE noun [countable]
[ Date: 1600-1700 ; Language: Latin ]
1 . technical the top or highest part of something pointed or curved:
the apex of the roof
the apex of a pyramid
2 . formal the most important position in an organization or society:
The king was at the apex of society.
3 . formal the most successful part of something SYN peak :
He was at the apex of his career.