Which of the following is NOT an essential element of a valid contract?

The essential elements of a valid contract typically include an offer, acceptance, consideration, and the capacity of the parties. While agreement may seem to encapsulate the idea of a mutual understanding between the parties, it is actually the interplay of offer and acceptance that constitutes a legally binding agreement.

In a contract, an offer initiates the possibility of the agreement, and acceptance signifies that the offer has been agreed upon. Consideration refers to something of value that is exchanged between the parties, which is crucial for the enforceability of the contract. Capacity is also critical, as it determines whether the parties have the legal ability to enter into a contract, typically assessing age and mental competence.

Thus, the term "agreement" is a broader concept that encompasses the specific elements of offer and acceptance. It is not identified as a standalone essential element in the technical formation of a contract, making it the correct choice as the element that is NOT necessary for a valid contract.