A Republic is a form of government in which the people or some portion thereof retain supreme control over the government, and in which the head of government is not a monarch. The word "republic" is derived from the Latin phrase res publica, which can be translated as "a public affair".
Both modern and ancient republics vary widely in their ideology and composition. The most common definition of a republic is a state without a monarch. In republics such as the United States and France, the executive is legitimized both by a constitution and by popular suffrage. In the United States, James Madison compared the republic to democracy, and found democracy wanting, due to the nature of democracies. Montesquieu included both democracies, where all the people have a share in rule, and aristocracies or oligarchies, where only some of the people rule, as republican forms of government. In modern political science, republicanism refers to a specific ideology that is based on civic virtue and is considered distinct from ideologies such as liberalism.
Most often a republic is a sovereign country, but there are also subnational entities that are referred to as republics, or which have governments that are described as "republican" in nature. For instance, Article IV of the Constitution of the United States "guarantee[s] to every State in this Union a Republican form of Government." The Soviet Union was a single nation composed of distinct and nominally sovereign Soviet Socialist Republics.
Niccolò Machiavelli described the governance and foundation of the ideal republic in his work Discourses on Livy. These writings, as well as those of his contemporaries such as Leonardo Bruni, are the foundation of the ideology political scientists call republicanism.
The idea of a republic first appeared in the writings of Italian scholars of the Renaissance, most importantly Machiavelli. Machiavelli divided governments into two types, principalities ruled by a monarch and republics ruled by the people.
In medieval Northern Italy a number of city states had commune or signoria based governments. In the late Middle Ages, writers, such as Giovanni Villani, began thinking about the nature of these states and the differences from the more common monarchies. These early writers used terms such as libertas populi to describe the states. The terminology changed in the 15th century as the renewed interest in the writings of Ancient Greece and Rome caused writers to prefer using classical terminology. To describe non-monarchial states writers, most importantly Leonardo Bruni, adopted the Latin word res publica.
While Bruni and Machiavelli used the term to describe the non-monarchial states of Northern Italy, res publica has a set of interrelated meanings in the original Latin. The term can quite literally be translated as "public matter". It was most often used by Roman writers to refer to the state and government, even during the period of the Roman Empire. The English word commonwealth derives from a direct translation of res publica, and its use in English is closer to how the Romans used the term res publica.
Today the term republic still most commonly means a system of government which derives its power from the people rather than from another basis, such as heredity or divine right. This remains the primary definition of republic in most contexts.
This bipartite division of government types differs from the classical sources, and also the earlier of Machiavelli's own works, which divided governments into three types: monarchy, aristocracy, and democracy. As Machiavelli wrote, the distinction between an aristocracy ruled by a select elite and a democracy ruled by a council appointed by the people became cumbersome. By the time Machiavelli began work on The Prince, he had decided to refer to both aristocracy and democracies as republics.
A further set of meanings for the term comes from the Greek word politeia. Cicero, among other Latin writers, translated politeia as res publica and it was in turn translated by Renaissance scholars as republic. This is not a very accurate translation and the term politeia is today usually translated as form of government or regime. One continued use of this archaic translation is the title of Plato's major work on political science. In Greek it was titled Politeia and in English is thus known as The Republic. This naming is preserved for historic reasons, but is not considered accurate. Within the text of modern translations of The Republic, alternative translations of politeia are used.
In English the word first came to prominence during The Protectorate era of Oliver Cromwell. While commonwealth was the most common term to call the new monarchless state, republic was also in common use.
Until modern times, the form of government for almost all states was monarchy. During the classical period the Mediterranean region was home to several states that are now known as the classical republics.
The concept of the "republic" itself was not a meaningful concept in the classical world. There are a number of states of the classical era that are today called republics by convention. These include the city states of ancient Greece such as Athens and Sparta and the Roman Republic. The structure and governance of these states was very different from that of any modern republic. There is a debate about whether the classical, medieval, and modern republics form a historical continuum. JGA Pocock has played a central role, arguing that there is a distinct republican tradition that stretches from the classical world to the present. Other scholars disagree. Paul Rahe, for instance, argues that the classical republics had a form of government with few links to those in any modern country.
The political philosophy of the classical republics has had a central influence on republican thought throughout the subsequent centuries. A number of classical writers discussed forms of government alternative to monarchies and later writers have treated these as foundational works on the nature of republics. Philosophers and politicians advocating for republics, such as Machiavelli, Montesquieu, Adams, and Madison, relied heavily on these sources.
Aristotle's Politics discusses various forms of government. One form Aristotle named politeia, which consisted of a mixture of the other forms. He argued that this was one of the ideal forms of government. Polybius expanded on many of these ideas, again focusing on the idea of mixed government. The most important Roman work in this tradition is Cicero's De re publica.
Over time the classical republics were either conquered by empires or became one themselves. Most of the Greek republics were annexed to the Macedonian Empire of Alexander. The Roman Republic expanded dramatically conquering the other states of the Mediterranean that could be considered republics, such as Carthaginian Republic. The Roman Republic itself then became the Roman Empire.