Most legislatures today are divided into two separate groups, called houses or chambers. A legislature of two chambers is called a bicameral legislature. In the United States, these two chambers are the Senate and the House of Representatives. In the United Kingdom, they are the House of Lords and the House of Commons. In Canada, they are the Senate and the House of Commons. In most two-house legislatures, both houses must approve a bill before it becomes a law. However, in the United Kingdom, only the approval of the House of Commons is necessary to pass any law relating to money matters.

In the U.S. Senate, each state, regardless of population, is equally represented. But members of the U.S. House of Representatives are divided among the states according to their population. Most state legislatures resemble the national legislature in organization and method of operating. But Nebraska has a one-house legislature chosen on the basis of population. A one-house body is known as a unicameral legislature. In 1964, the Supreme Court of the United States ruled that representation in both houses of state legislatures must be based on population.