In American English, the definition of a republic refers specifically to a form of government in which elected individuals represent the citizen body and exercise power according to the rule of law under a constitution, including separation of powers with an elected head of state, referred to as a Constitutional republic or representative democracy.
As of 2017, 159 of the world's 206 sovereign states use the word "republic" as part of their official names – not all of these are republics in the sense of having elected governments, nor is the word "republic" used in the names of all nations with elected governments. While heads-of-state often tend to claim that they rule only by the "consent of the governed", elections in some countries have been found to be held more for the purpose of "show" than for the actual purpose of in reality providing citizens with any genuine ability to choose their own leaders.
The term republic was first coined c. 500 BC in Rome, but over time the term has undergone several changes in meaning. Initially the Latin term res publica signified the earlier "partial form of democracy" as found in Rome from c. 500 BC until c. 27 BC. In this early Roman partial-democracy, the power of the aristocratic or patrician class who held all of the seats in the Roman Senate, was checked by the institution of the consulship, whose two consul/vice-rulers were elected annually by the free citizens or plebes of Rome. The ancient Roman definition of the word differs from the modern use of the term, where no leadership positions are held to be restricted to only the "ruling class".
Most often a republic is a single sovereign state, but there are also sub-sovereign state entities that are referred to as republics, or that have governments that are described as "republican" in nature. For instance, Article IV of the United States Constitution "guarantee to every State in this Union a Republican form of Government". In contrast, the former Soviet Union, which described itself as being a group of "Republics" and also as a "federal multinational state composed of 15 republics", was widely viewed as being an authoritarian form of government and not as a republican form of government. It was seen as authoritarian, as its electoral system was structured so as to automatically guarantee the election of government-sponsored candidates.
The term originates as the Latin translation of Greek word politeia. Cicero, among other Latin writers, translated politeia as res publica and it was in turn translated by Renaissance scholars as "republic" (or similar terms in various western European languages).