Essence of the contract

Definition of 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.” See also Basis of bargain.

That's the definition of Essence of the contract in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.