1. Cause is an action or event that brings about or contributes to a specific outcome. In legal actions, there are a variety of different variations of cause, for example, “but-for cause,” “proximate cause,” “cause in fact” and “intervening cause.” Cause is a necessary element in most legal actions. 2. A “cause of action” is a civil case. 3. “Probable cause” is a burden of proof that is required for police officers to make an arrest, conduct a search of a person or his property or obtain a search warrant.