IPA: /ɒmˈnɪʃəntli/
KK: /ɑmˈnɪʃəntli/
In a way that shows complete knowledge or understanding of everything.
The narrator told the story omnisciently, revealing the thoughts and feelings of all the characters.
Omnisciently → It is formed from "omni-" (meaning all) and "scientia" (meaning knowledge) with the adverbial suffix "-ly" (meaning in a manner). The word "omnisciently" means in a manner that possesses all knowledge or knowing everything.
Think of 'all' ('omni-') and 'knowledge' ('scientia') to remember that 'omnisciently' means knowing everything.