What is the meaning of 'Apex'?

Apex (noun): 
English Meaning: The top or highest part of something. 
Bangla Meaning: উচ্চতম বিন্দু; শীর্ষবিন্দু: the apex of a triangle; the apex of one’s career/fortunes.

Synonyms: Pinnacle (সূচাগ্র,), Peak (সর্বোচ্চ), Highest (শীর্ষ), Maximum, Top(চূড়া)। 
Antonyms: Base(ভিত্তি), Nadir(সর্বনিম্ন), Bottom (তলা), Minimum(সামান্যতম), Lowest (সর্বনিম্ন)। 
Other Forms: Apical (adjective). 
Example Sentence: 
1. At 37, she'd reached the apex of her career.
2. She reached the apex of fame, only to find it wasn't what she expected. 

Source: Website lecture.