Bicameralism
In government, bicameralism is the practice of having two legislative or parliamentary chambers. Thus, a bicameral parliament or bicameral legislature is a parliament or legislature which consists of two Chambers or Houses.The ideas which underlie bicameralism may be traced back to the theories developed in ancient Greece and Rome, though recognisable bicameral institutions arose first in medieval Europe where they were associated with separate representation of different estates of the realm. The American Founding Fathers eschewed any notion of separate representation for a social aristocracy, but accepted the prevailing disposition towards bicameralism. However, they then invented a new rationale for bicameralism linked with federalism. In subsequent constitution making, federal states have invariably adopted bicameralism, and they are popular when regional differences or sensitivities require more explicit representation. but the older justification for second chambers as providing opportunities for second thoughts about legislation has survived. A trend towards unicameralism in the twentieth century appears now to have been halted. Growing awareness of the complexity of the notion of representation and the multifunctional nature of modern legislatures may be affording incipient new rationales for second chambers though these do generally remain contested institutions in ways that first chambers are not.
The relationship between the two Chambers varies; in some cases, they have equal power, while in others, one Chamber is clearly superior in its powers. It is also commonplace in most federal systems to have a bicameral legislature, with the second chamber representing the constitutent states, such as the United States Senate
Some political scientists believe that bicameralism makes meaningful political reforms more difficult to achieve and increases the risk of deadlock (particularly in cases where both chambers have similar powers). Others argue strongly for the merits of the 'checks and balances' provided by the bicameral model, which they believe helps prevent the passage into law of ill-considered legislation.
Examples
See also: Upper House, Unicameralism, List of national legislatures