If performance of a contract is not substantial, there is a material breach, which excuses the nonbreaching party from performance.

Material Breach

A significant violation or failure to meet a contractual agreement, justifying termination of the contract by the other party.

Substantial

Of considerable importance, size, or worth; significantly large or of a degree that merits attention.

Nonbreaching Party

The party in a contractual agreement that has not failed to fulfill their obligations as set forth in the contract.