That which is the most important and indispensable nature of sommething. The gist. That which is indispensable to that of which it is the essence. Essence of the contract. Any condition or stipulation in a contract which is mutually understood and agreed by the parties to be of such vital importance that a sufficient performance of the contract cannot be had without exact compliance with it is said to be “of the essence of the contract.”
ESSENCE
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.