apex 
/ˈeɪˌpɛks/ noun
plural apex·es /ˈeɪˌpɛks/ noun [count] : the top or highest point of something — usually singular ▪ the mountain's apex [=peak, summit] — usually used figuratively ▪ Tragically, she died at the apex [=acme, high point] of her career/fame. ▪ The excitement was about to reach its apex.
