The common law is a kind of legal system. Under the common law, the law is not just made by legislation (laws created by the government) but also by the courts. As a result, some laws and legal ideas may be created through the courts without the government playing a role. Common-law courts use the precedent of earlier courts to help them make decisions.
The common law is used in the United Kingdom and most countries that used to be colonies of the British Empire, including the United States. Many other countries use a system called civil law, where people say that legislation is the only kind of law. In common law countries, courts usually have more power than in civil law countries.
Common law started in England when courts decided to use tradition, custom, and precedent to help them make decisions. A precedent is something that another court has done in the past. By looking at decisions by earlier court, a common-law court tries to make decisions that will not surprise people and that fit in with the rest of the law.
In common law countries, when people like lawyers and judges want to know what the law is, they also look at what courts have written. When a court decides a case, it makes a decision and then usually delivers a judgment or a an opinion about what the law is. A judgment or court's opinion explains how the court reached its decision, and it is a guide for later courts that need to decide similar cases. The case sets a precedent. The judgments of higher courts will commonly tell lower courts how they must decide a case on the same or very similar facts - if so, the precedent is said to be "binding". Even if the facts are different, the reasoning in the case may still be considered by the court as "persuasive".
Even though courts follow precedent, legislation is still important in common-law countries. In fact, it is usually more powerful than precedent. For example, if legislation and precedent say different or opposite things, a court will usually have to follow the legislation.
In common-law countries, many important areas of law are mostly made by precedent. For example, in England and Wales and in most states of the United States, the law of contracts and torts is mostly made by precedent.
Different meanings [change]
In a common-law country, sometimes the words common law are used to mean the law that the courts have made. For example, a lawyer or judge might say that a case can be decided using "only common law." This means that no legislation helps decide the case.
The words common law also sometimes mean the system of law that existed in England in the 1700s and 1800s. At that time, England had two different court systems. One was called equity and one was called common law. Law was mostly for ordering people to pay money, and equity was mostly for other kinds of cases. Today, in most places, there are not two separate systems, and courts sometimes say that they work with both common law and equity.