e s s e n c e

ˈesəns/

noun

noun: essence

1. the intrinsic nature or indispensable quality of something, especially something abstract, that determines its character; 
   power of something without which it would not exist or be what it is.

   see also:

   quintessence, soul, spirit, nature;

   core, heart, crux, nucleus, substance; 

   principle, fundamental quality, sum and substance.