When one party fails to fulfill their part of a contract, this is referred to as:

The term "Breach" specifically refers to the failure of one party to fulfill their obligations as stipulated in a contract. In the realm of contracts, a breach occurs when one party does not perform their duties as agreed, which can include not delivering goods, not making payments, or failing to provide services as outlined. This concept is fundamental in contract law, as it determines the rights of the non-breaching party, including the right to seek damages or other remedies.

Disaffirmance involves the cancellation of a contract, generally applicable in situations where one party wants to void the contract due to some incapacity or issue at formation. Nullification refers to making something void or invalid, often used in legal contexts to indicate that a law or statute has no effect. Termination involves ending a contract by mutual agreement or under specific circumstances as defined within the contract itself.

Understanding these distinctions highlights why "Breach" accurately defines the situation wherein a party fails to meet their contractual obligations, thereby enabling the other party to take appropriate action.