A penalty clause is a provision in a contract that imposes a monetary or other punishment on a party for failing to fulfill specific terms of the agreement. These clauses are typically designed to deter breach of contract and to encourage parties to perform their obligations as agreed. However, in many jurisdictions, penalty clauses are generally unenforceable if they are deemed excessive or disproportionate to the actual harm caused by the breach. Instead, the law often favors liquidated damages clauses, which compensate the injured party for a genuine pre-estimate of the loss.