In government, bicameralism is the practice of having two legislative or parliamentary chambers. The relationship between the two chambers of a bicameral legislature can vary. In some cases, they have equal power, and in others, one chamber is clearly superior to the other. It is commonplace in most federal systems to have a bicameral legislature. The United States, for example, has a bicameral legislature in which one chamber, the Senate, has an equal number of members representing each constituent state, and the members of the other chamber, the House of Representatives, number according to each state's population.
Some political scientists believe that having a bicameral legislature makes meaningful political reforms more difficult to achieve and increases the risk of deadlock. This risk is greater in cases when both chambers have equal powers. Other political analysts argue strongly for the merits of the checks and balances that are provided by the bicameral model, which they believe helps prevent ill-considered legislation from being passed into law.
As of 2011, more than 20 countries had bicameral legislatures. Many other countries have unicameral legislatures, which consist of single legislative houses. The term "bicameral" comes from Latin and combines bi, which means "two", with camera, which means "chamber." "Unicameral" substitutes uni, or "one," for bi.
Partial List of Countries That Have Bicameral Legislatures:
| Country | Type | Legislative chambers |
| Afghanistan | National Assembly | Wolesi Jirga and Masharano Jirga |
| Australia | Parliament | House of Representatives and Senate |
| Canada | Parliament | House of Commons and Senate |
| France | Parliament | National Assembly and Senate |
| Germany | no single term | Bundestag and Bundesrat |
| India | Parliament | Lok Sabha (House of the People) and Rajya Sabha (Council of States) |
| Mexico | Congress | Chamber of Deputies and Senate |
| Pakistan | Parliament | National Assembly and Senate |
| Republic of Ireland | Oireachtas | Dáil Éireann (House of Representatives) and Seanad Éireann (Senate) |
| United Kingdom | Parliament | House of Commons and House of Lords |
| United States | Congress | House of Representatives and Senate |
In addition, many regional or local legislative bodies also are bicameral. In the United States, for example, all of the state legislatures except Nebraska's are also bicameral. In Australia, all of the state parliaments except Queensland's are also bicameral.
