Res publica in the context of "Vowel length"

A republic, based on the Latin phrase res publica ('public thing' or 'people's thing'), is a state in which political power rests with the public (people), typically through their representatives—in contrast to a monarchy. Although a republic is most often a single sovereign state, subnational state entities that have governments that are republican in nature may be referred to as republics.

Representation in a republic may or may not be freely elected by the general citizenry. In many historical republics, representation has been based on personal status and the role of elections has been limited. This remains true today; among the 159 states that use republic in their official names as of 2017, and other states formally constituted as republics, are states that narrowly constrain both the right of representation and the process of election.

Rzeczpospolita (pronounced [ʐɛt͡ʂpɔsˈpɔlita] ) is a traditional Polish term for a political community founded for the common good. Rzeczpospolita is the historic name of Poland, Polish - Lithuanian Commonwealth. In Poland, in modern era Rzeczpospolita refers exclusively to the Republic of Poland and it is the official name of Poland, Rzeczpospolita Polska in Polish language. The noun "rzeczpospolita", meaning "public welfare, general good or advantage" rzecz "thing, matter" and pospolita "common", is analogous to the Latin rēs pūblica (rēs "thing" + pūblica "public, common"), i.e. republic, in English also rendered as commonwealth for example, Polish- Lithuanian Commonwealth), and modern term in English us republic and referend to all modern democracies,republucs, for instance, French Republic.

In modern Polish, the word rzeczpospolita is used exclusively in relation to the Republic of Poland, while any other republic is referred to in Polish as a republika (e.g. Italian Republic – Republika Włoska).

A commonwealth is a traditional English term for a political community founded for the common good. The noun "commonwealth", meaning "public welfare, general good or advantage", dates from the 15th century. Originally a phrase (the common-wealth or the common wealth – echoed in the modern synonym "public wealth"), it comes from the old meaning of "wealth", which is "well-being", and was deemed analogous to the Latin res publica. The term literally meant "common well-being". In the 17th century, the definition of "commonwealth" expanded from its original sense of "public welfare" or "commonweal" to mean "a state in which the supreme power is vested in the people; a republic or democratic state".

The term evolved to become a title to a number of political entities. Three countries – Australia, the Bahamas, and Dominica – have the official title "Commonwealth", as do four U.S. states and two U.S. territories. Since the early 20th century, the term has been used to name some associations of states, most notably the Commonwealth of Nations, an organisation primarily of former territories of the British Empire. It is also used in the translation for the organisation made up of formerly Soviet states, the Commonwealth of Independent States.

In Ancient Rome, a civitas (Latin pronunciation: [ˈkiːwɪtaːs]; plural civitates), sometimes translated as "city", was the social body of the cives, or citizens, united by their laws, which gave them responsibilities (Latin: munera) on the one hand, and rights on the other. The agreement (concilium) has a life of its own, creating a res publica or "public entity" (synonymous with civitas), into which individuals are born or accepted, and from which they die or are ejected. The civitas is not just the collective body of all the citizens; it is the contract binding them all together, because each of them is a civis.

Commonwealth is a term used by four of the 50 states of the United States in their full official names: Kentucky, Massachusetts, Pennsylvania, and Virginia. "Commonwealth" is a traditional English term used to describe a political community as having been founded for the common good, and shares some similarities with the Latin phrase "res publica" ('the public thing'), which ultimately is the origin of the word "republic".

The "commonwealth" appellation is merely stylistic and carries no legal or political significance. The four states that use this term are all in the Eastern United States, and prior to the formation of the United States in 1776 were British colonial possessions (at the time, Kentucky was a part of colonial Virginia). As such, they share a strong influence of English common law in some of their laws and institutions.