The law is a set of rules that regulate behavior and govern society. It can be used to protect people and things, maintain order, promote social justice, or change the course of history (e.g., during colonialism, when European nations imposed their laws on countries they conquered). Different systems of law serve these goals differently. For example, an authoritarian government might keep the peace and maintain the status quo, but it may also oppress minorities or suppress dissent.

Law can refer to the legal field, which includes all professions that advise people about their rights and represent them in court. It can also refer to the rules that govern how a country functions, such as contracts, torts, property, and criminal law. It can even refer to the governing body itself, such as Congress or a local city council.

In science, a law is an indisputable fact that describes the way the world and the forces in it work. Laws don’t explain why things happen, however; that’s the job of scientific theories. For example, the law of conservation of energy states that a system’s total amount of energy is constant. In the United States, a bill becomes a law when it’s passed by both the House of Representatives and the Senate. The President can sign the bill into law or reject it with a veto. If Congress wants to bypass the veto, they can pass the bill again with a two-thirds majority vote in both houses.