Law is a set of rules created and enforced by social or governmental institutions to regulate behavior. The precise definition of law is a matter of longstanding debate. It includes law devised by man which he deems to be in his best interests as well as laws established by natural processes such as the laws of gravity and the laws of genetic inheritance.
Law serves many purposes, but there are four principal ones: establishing standards, maintaining order, resolving disputes and protecting liberties and rights. It is essential that government and private actors are held accountable for their actions, that the rules governing them are clear, publicized, stable and applied evenly.
Moreover, laws can have both descriptive and prescriptive elements: they describe the observation that certain natural processes always lead to particular outcomes (such as Newton’s Law of Gravity or Mendel’s Law of Independent Assortment) and also tell us what we ought to do (e.g., obey the speed limit or donate blood).
Modern legal systems are distinguished by two main categories: civil law and common law. Civil law systems, which are found in about 60% of the world’s nations, derive from a combination of legislation (laws passed by governments) and traditional sources of law including custom and case law. Common law systems, which are found in most other nations, are largely derived from English law and its evolution through courts over time. Common laws include contracts, torts, property and criminal law.