An act in law can refer to different concepts depending on the context. In general, an act is an instrument that records a fact or something that has been said, done, or agreed. Acts generally take the form of legal instruments of writing that have probative value and executory force). In the context of legislation, an act is a formal body of law, and it can create a new law or change an existing law. For example, in the United States, laws are also known as Acts of Congress, and when the president signs a bill, it becomes a law. In the criminal law context, an act is part of the concept of actus reus and refers to a voluntary bodily movement or a term for a body of law/proposed law. It is a prerequisite to finding a defendant guilty, and a breach of a duty to act, known as an omission, can also satisfy the actus reus requirement. Therefore, an act in law can encompass a range of meanings, from a formal body of law to a voluntary bodily movement or something done by a person in accordance with their free will.