Define "mistake," "mutual mistake," and "unilateral mistake." Explain how the law treats mutual and unilateral mistakes

A mistake is a belief that is not in accord with the facts. Mutual mistake occurs when both parties are mistaken as to the same set of facts, and unilateral mistake occurs when only one of the parties is mistaken. If a mutual mistake relates to a basic assumption on which a contract is formed and it has a material effect on the agreed exchange, it is voidable by the adversely affected party unless that party bears the risk of the mistake. Courts are hesitant to grant relief for a unilateral mistake even if it relates to a basic assumption on which the party entered into the contract and it has a material effect on the agreed exchange.