In ancient Rome, the Latin term (pl. ) referred to a town or city. Etymologically, the was a social contract among ("duty holders"), or citizens of the town. The duties () were a communal obligation assumed by the in exchange for the privileges and protections of citizenship. Every citizen was a . The distinction of was not made in the Roman Kingdom; instead, the immediate neighbours of the city were invited or compelled to transfer their populations to the urban structure of Rome, where they took up residence in neighbourhoods and became Romans per se. Under the Roman Republic the practical considerations of incorporating communities into the city-state of Rome forced the Romans to devise the concept of , a distinct state under the jurisdiction of Rome. It was necessary to distinguish various types of and other settlements, such as the colony. In the early Roman Empire these distinctions began to disappear; for example, when Pliny the Elder served in the Roman army, the distinctions were only nominal. In the final stage of development, all citizens of all cities and towns throughout the empire were equally citizens of Rome. The then simply meant municipality, the lowest level of local government. Creation of a municipium The munera and the citizenship and its rights and protections were specific to the community. No matter where a person lived, at home or abroad, or what his status or class, he was a citizen of the locality in which he was born. The distinguishing characteristic of the municipium was self-governance. Like any ancient city-state, the municipium was created by an official act of synoecism, or founding. This act removed the sovereignty and independence from the signatory local communities, replacing them with the jurisdiction of a common government. This government was then called the res publica 'public affair' or in the Greek world the koinon 'common affair'. The term municipium began to be used with reference to the city-states of Italy brought into the city-state of Rome but not incorporated into the city. The city of Romulus synoecised the nearby settlements of Latium, transferring their populations to the seven hills, where they resided in typically distinct neighbourhoods. And yet, Sabines continued to live in the Sabine Hills and Alba Longa continued even though synoecised. The exact sequence of events is not known, whether the populace was given a choice or the synoecised sites were reoccupied. As