What Is a Bicameral System?

A bicameral system is a reference to a government with two legislative houses or chambers. Bicameral is the Latin word that describes a two-house legislative system. The bicameral system originated in England, and the U.S. adopted that system upon its founding. 

The U.S. federal government uses a bicameral system, as do all of the U.S. states, with the exception of Nebraska. U.S. cities, by contrast, commonly use the unicameral system like Nebraska. 

Key Takeaways

  • A bicameral system is a government style with two separate divisions within the legislative branch of government, versus a unicameral system that does not divide the government branch.
  • The U.S. bicameral system is divided into the House of Representatives (where the number of members allocated is based on state population) and the Senate (where each state gets two members).
  • The majority of international governments use the unicameral system—with a roughly 60/40 split between unicameral and bicameral.
  • Each house of the legislative branch has differing powers to ensure there are checks and balances within the system. 
  • The more populous House of Representatives branch has less stringent requirements for members when it comes to age and citizenship length compared to the Senate.

How a Bicameral System Works

The bicameral system in the U.S. consists of the House of Representatives and the Senate—collectively known as Congress. Article 1, Section 1 of the U.S. Constitution establishes the Congress consisting of the Senate and House of Representatives. There are both historical and practical reasons to have two houses of the legislature. 

In the U.S., the historical reason is that during the Constitutional Convention America’s founders could not agree on whether the states should each have the same number of representatives or whether the number of representatives should be based on population. The founders decided to do both in an agreement known as the Great Compromise, and thus the bicameral system we know today was established. 

A practical reason for a bicameral system is to prevent the legislative branch from having too much power—an intrabranch check. The bicameral system is supposed to provide for checks and balances and prevent potential abuses of power.

The U.S. bicameral system arose from a desire to have a balanced system within the legislative branch and to address a disagreement over how states would be allocated representation.

Special Considerations 

Worldwide, about 41% of governments are bicameral and about 59% are unicameral. Other countries that have a bicameral system include Australia, Brazil, Canada, Germany, India, the U.K., Ireland, the Netherlands, Russia, Spain, and the Czech Republic. The size, term of office, and method of election (directly elected, indirectly elected, appointed, or other) for each chamber of a bicameral system will vary by country. Unicameral systems became more popular during the 20th century, and some countries, including Greece, New Zealand, and Peru, switched systems from bicameral to unicameral.

In the U.K., the bicameral system consists of the House of Lords and the House of Commons. The House of Lords represents a smaller, more elite class, while the House of Commons represents a larger, more ordinary class. The U.S. system was unique when it was established in that it was not intended to represent members of different classes but residents of different locations.

Requirements for a Bicameral System

Members of the U.S. House of Representatives serve two-year terms. Two-year terms are meant to keep representatives responsive to voters’ needs. There are 435 representatives in total, with the number from each state being in proportion to that state’s population. This system is called proportional representation. Alabama, for example, has seven representatives, while California has 53. The seven least-populous states—Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont, and Wyoming—have only one representative each. 

Each state also has two Senators (a system called equal representation) who are directly elected by voters and serve six-year terms. Before the Seventeenth Amendment to the Constitution was ratified in 1913, the state legislatures got to choose Senators, who tended to be elites.

Each house has different requirements to serve. To be a U.S. representative, you must be at least 25 years old, a U.S. citizen for at least seven years, and a resident of the state you want to represent. To be a U.S. Senator, you must be at least 30 years old, a U.S. citizen for at least nine years, and a resident of the state you want to represent.

Each house also has unique powers. Only members of the House can criminally indict (impeach) the president and other federal officials; the Senate then reviews the case. The House also decides presidential elections if no candidate wins a majority of electoral college votes. And any bill that increases taxes originates in the House, which is why the House is said to have the power of the purse. The Senate votes to confirm the appointment of more than 1,000 executive officers, and it can ratify treaties with a two-thirds vote.