一个单一的系统是一种政府的权力集中在中央政府，虽然许多断言，没有一个单一的系统的特定的定义。单一国家是一个独立的国家，它是中央政府最高的一个孤立的要素，任何行政部门都实行中央政府决定委派的权力。单一制是政府最为常见的类型，众多国家都使用该制度。它发生在自治和非自治的国家。许多欧洲国家都有单一的政府，虽然一些国家，如比利时，德国，瑞士，波斯尼亚，奥地利和俄罗斯没有一个单一的政府。中央政府在一个统一的系统中负责组织在国家一级，如外交事务，国家经济政策和国防的问题。中央领导或是使决策的机构管理着所有权力的所有特征，因为没有权力可以被合法地设置为其他权力阶段。政府的所有地区都是在一个机构的权力下，因此，有一个单一的系统通常有更一致的法律和政策比联盟。根据John Markley的说法，大多数政府基于Westminster系统都是统一的，虽然加拿大、澳大利亚、印度和马来西亚的联邦宪法（John Markley 2部）。并不是所有的政府在单一制国家的决定都是由权力的持有人。单一的政府也给行政权力的地方政府在这一过程被称为转移，这往往是建立适应民族或少数民族语言的渴望更大的自主权（John Markley 2部）。并不是所有的政府在单一制国家的决定都是由权力的持有人。一个单一的系统的一些特性，国家是不允许退出中央政府，国家不允许通过任何立法，出现相对的公共政策或联邦政府的规定，由国家立法议会创建规则限制了国家的权力，通过立法的中央政府创造的规则是有效的每一个状态。
A unitary system is a form of government where power is focused among the central government, although many assert that there is no particular definition for a unitary system. A unitary state is an independent state which is governed as one solitary element where the central government is highest and any administrative division implements powers that the central government decides to delegate. The unitary system is the most common type of government, and numerous states use this system of government. It takes place in both self-governing and non self-governing nations. Many European nations have unitary governments although some nations such as Belgium, Germany, Switzerland, Bosnia-Herzegovina, Austria and Russia do not have a unitary government. The central government in a unitary system is accountable for organizing matters at that national level such as foreign affairs, national economic policy, and national defense. The central leader or the body that makes decisions regulates all characteristics of supremacy, since there is no authority lawfully set aside for other stages of power. All regions of government are under the power of one body, so nations that have unitary systems usually have more consistent laws and policies than alliances. According to John Markley, Most governments based on the Westminster system are unitary, although Canada, Australia, India and Malaysia have federal constitutions (John Markley, pars 2). Not all government decisions in unitary states are made by the holder of power. Unitary governments also give executive power to local authorities in a process called devolution, which often is instituted to accommodate ethnic or linguistic minorities who desire greater autonomy (John Markley, pars 2). Not all government decisions in unitary states are made by the holder of power. Some characteristics of a unitary system are that states are not allowed to withdraw from the central government, states are not allowed to pass any legislation that appears opposing to public policy or the rules of the union government, rules created by the legislative assembly of the state are limited to the authority of the state, and rules created by legislation by the central government are valid to every state.
A federal system is a system where power is separated between a central government and various local governments. In America the U.S. constitution established Federalism which is a form of political association where lawmaking power is separated between a central government. In the United States it is separated amongst the national, state, and local governments. This system permits the government to have divided rights and authorities. Many countries such as Germany, Australia, Brazil, the United States, and Canada function using a federal government. Federal systems can sometimes be argumentative because it is uncertain how much power the government should be awarded. Federal systems permit powers that concern the entire nation. For example, in many countries that have a federal system, only the national government can announce war on another country. Switzerland had some controversy when setting up their direct democracy system. In Brazil, the federal system was passed by an official order then by a military coup.