Definition from Nolo’s Plain-English Law Dictionary

Factual evidence that helps to establish that an event occurred or a statement is true. When someone is accused of a crime, the government must prove every element, or aspect, of the crime, such as who physically committed the act and whether that person did so with the intent to commit the crime. Unless all elements of the charged crime are proved, the prosecution will not prevail. In civil cases, too, the plaintiff must prove every aspect of the complaint. (See also: burden of proof)

Definition provided by Nolo’s Plain-English Law Dictionary.