A legislature is a governmental deliberative body with the power to adopt laws. Legislatures are known by many names, including: parliament, congress, diet and national assembly. In parliamentary systems of government, the legislature is formally supreme and appoints the executive. In presidential systems of government, the legislature is considered a branch of government which is equal to, and independent of, the executive. In addition to enacting laws, legislatures usually have exclusive authority to raise taxes and adopt the budget and other money bills. The consent of the legislature is also often required to ratify treaties and declare war.
The primary component of a legislature is one or more chambers or houses: assemblies that debate and vote upon bills. Most legislatures are either bicameral or unicameral. A unicameral legislature is the simplest kind of law-making body and has only one house. A bicameral legislature possesses two separate chambers, usually described as an upper house and a lower house, which may differ in duties, powers, and methods for the selection of members.
In most parliamentary systems, the lower house is the most powerful house while the upper house is merely a chamber of advice or review. However in presidential systems the powers of the two houses are often similar or equal. In federations it is typical for the upper house to represent the component states. For this purpose the upper house may either contain the delegates of state governments, as is the case of Germany and was the case in the pre-19 century United States, or to be elected according to a formula that grants disproportionate representation to smaller states, as is the case today in Australia and the United States. Historically, as well as bicameral and unicameral bodies, there have also been rare instances of tricameral legislatures.
Many legislatures are said to include not just one or more houses but also the head of state. This is because in most systems it is necessary that, after being approved by the house or houses of the legislature, a bill receive the assent of the head of state before it can become law. This may be the case even if, as is the case in many parliamentary systems, the assent of the head of state is merely a formality and will not be withheld. It is also common, however, for the head of state not to be considered a formal part of the legislature, even if they have the power to veto laws. The British Parliament formally consists of the Crown, and two houses; similarly, the Irish Oireachtas consists officially of the President and two houses. In contrast, the United States Congress consists only of its two houses and does not officially include the US president, despite the fact that he wields a veto.
The power of legislatures varies widely from country to country. Rubber stamp legislature is a derogatory name for a legislature that has no real power but simply approves, by unanimous or near unanimous votes, bills put before it by other institutions. For example, the legislatures of many Communist states were often derided as mere 'rubber stamps' for decisions of the ruling party. The term is not usually used to describe legislatures of parliamentary systems. Although the final draft of legislation introduced by the government almost always passes, these legislatures are generally not labelled 'rubber stamps' because legislators are involved in the drafting and amendment of bills.