Fraud undermines legal acts and renders tainted transactions void, including fraud on court leading to nullification. Fraud is a knowing misrepresentation, concealment of a material fact, or reckless misrepresentation made to induce another to act detrimentally, and also includes unconscionable dealing and other willful or reckless conduct that improperly advantages one party. Fraud vitiates legal acts: misrepresentation can amount to deceit, and acts tainted by fraud, including collusion or suppression of material facts and fraud on the court, may render transactions void ab initio and defeat equitable doctrines.