Common law is a body of law created by judges and similar quasi-judicial tribunals by virtue of being stated in written opinions. It is also known as judicial precedent, judge-made law, or case law. The defining characteristic of common law is that it arises as precedent, meaning that common law courts look to previous decisions made by judges and similar tribunals when making their own decisions. Common law is derived from judicial decisions instead of from statutes.

Some key features of common law include:

• Flexibility: Common law has been described as flexible, since it can respond to changes in society. Unlike civil law systems, common law doesn’t require lawmakers to pass changes in statutes and codes, which can take a long time or never happen at all. When it comes to common law, higher courts can overrule prior decisions as “bad law” and they don’t need to wait for lawmakers to do it for them.

• Precedent: Common law is based on legal precedents established by the courts. If a court makes a particular decision based on a specific set of facts, then the court is required to follow that decision if they ever must make a ruling on the same or closely related issue. Likewise, decisions made by higher courts are typically binding on lower courts in the same jurisdiction.

• Evolution: Common law evolves daily and immediately as courts issue precedential decisions, and all parties in the legal system are responsible for up-to-date knowledge. There is no fixed reference point for the definition of "common law", except in a handful of isolated contexts.

Common law is still used today in several countries around the world, including the U.S., Canada, India, and Australia. In the U.S., common law is used at both the state and federal levels. In some instances, common law may differ between districts.

Common law marriage is a legal framework that may allow couples to be considered married without having formally registered their union as either a civil or religious marriage. While common law is not common among the U.S., there are a number of states that have statutes or allow for common law marriage if they meet certain requirements.