The judiciary (also known as the judicial system or court system) is the system of courts that interprets and applies the law in the name of the state. The judiciary also provides a mechanism for the resolution of disputes. Under the doctrine of the separation of powers, the judiciary generally does not make law (that is, in a plenary fashion, which is the responsibility of the legislature) or enforce law (which is the responsibility of the executive), but rather interprets law and applies it to the facts of each case. This branch of the state is often tasked with ensuring equal justice under law. It usually consists of a court of final appeal (called the "Supreme court" or "Constitutional court"), together with lower courts.

In many jurisdictions the judicial branch has the power to change laws through the process of judicial review. Courts with judicial review power may annul the laws and rules of the state when it finds them incompatible with a higher norm, such as primary legislation, the provisions of the constitution or international law. Judges constitute a critical force for interpretation and implementation of a constitution, thus de facto in common lawcountries creating the body of constitutional law.

In the US during recent decades the judiciary became active in economic issues related with economic rights established by constitution because "economics may provide insight into questions that bear on the proper legal interpretation".^[3] Since many countries with transitional political and economic systems continue treating their constitutions as abstract legal documents disengaged from the economic policy of the state, practice of judicial review of economic acts of executive and legislative branches have begun to grow.

In the 1980s, the Supreme Court of India for almost a decade had been encouraging public interest litigation on behalf of the poor and oppressed by using a very broad interpretation of several articles of the Indian Constitution.^[4]

Budget of the judiciary in many transitional and developing countries is almost completely controlled by the executive. The latter undermines the separation of powers, as it creates a critical financial dependence of the judiciary. The proper national wealth distribution including the government spending on the judiciary is subject of the constitutional economics. It is important to distinguish between the two methods of corruption of the judiciary: the state (through budget planning and various privileges), and the private.^[5]

The term "judiciary" is also used to refer collectively to the personnel, such as judges, magistrates and other adjudicators, who form the core of a judiciary (sometimes referred to as a "bench"), as well as the staffs who keep the system running smoothly.