Actual injury refers to the real, tangible harm or damage that a person suffers as a result of an action or decision, particularly in the context of legal claims. This concept is crucial in determining whether a plaintiff has standing to sue, as it establishes that there is a concrete stake in the outcome of the case. In the realm of judicial power, actual injury is tied to constitutional and prudential limitations, which dictate the ability of courts to hear cases based on the existence of a legitimate injury.