In law, the judiciary or judicial system is the system of courts which administer justice in the name of the sovereign or state, a mechanism for the resolution of disputes.

The term is also used to refer collectively to the judges, magistrates and other adjudicators who form the core of a judiciary, as well as the support personnel who keep the system running smoothly. Under the doctrine of the separation of powers, 'the judiciary is the branch of government primarily responsible for interpreting the law'Fact: date=July 2008. It construes the laws enacted by the legislature.

• In common law jurisdictions, courts interpret law, including constitutions, statutes, and regulations. They also make law based upon prior case law in areas where the legislature has not made law. For instance, the tort of negligence is not derived from statute law in most common law jurisdictions. The term common law refers to this kind of law.
• In civil law jurisdictions, courts interpret the law, but are, at least in theory, prohibited from creating law, and thus, still in theory, do not issue rulings more general than the actual case to be judged. In practice, jurisprudence plays the same role as case law.
• In socialist law, the primary responsibility for interpreting the law belongs to the legislature.

This difference can be seen by comparing United States, France and the People's Republic of China:

• in the United States government, the Supreme Court is the final authority on the interpretation of the federal Constitution and all statutes and regulations created pursuant to it;
• in France, the final authority on the interpretation of the law is the Conseil d'État for administrative cases, and the Court of Cassation for civil and criminal cases;
• and in the PRC, the final authority on the interpretation of the law is the National People's Congress.
• Other countries such as Argentina have mixed systems that include lower courts, appeals courts, a cassation court (for criminal law) and a Supreme Court. In this system the Supreme Court is always the final authority but criminal cases have four stages, one more than civil law.

It is said that the famed Byzantine Emperor Justinian had the Corpus Juris Civilis compiled and all other decisions by jurists burned to create certainty in the law. Again in the 19th century, French legal scholars at the time of the development of the Code Napoléon advocated the same kind of approach — it was believed that since the law was being written down precisely, it should not need interpretation; and if it did need interpretation, it could be referred to those who wrote the code. Napoleon, who was an advocate of this approach, felt that the task of interpreting the law should be left with the elected legislature, not with unelected judges. This contrasted with the pre-revolutionary situation in France, where unelected 'parliaments' defending the interests of the nobility would often slow the enforcement of royal decisions, including much needed reforms.