Provinces were generally governed by politicians of senatorial rank, usually former consuls or former praetors. A later exception was the province of Egypt, incorporated by Augustus after the death of Cleopatra: it was ruled by a governor of equestrian rank only, perhaps as a discouragement to senatorial ambition. This exception was unique, but not contrary to Roman law, as Egypt was considered Augustus' personal property, following the tradition of earlier, Hellenistic kings.
The Latin term provincia also had a more general meaning, 'jurisdiction'.
The Latin word provincia originally meant any task or set of responsibilities assigned by the Senate to an individual who held imperium ("right of command"), which was often a military command within a specified theater of operations. Under the Roman Republic, the magistrates were elected to office for a period of one year, and those serving outside the city of Rome, such as consuls acting as generals on a military campaign, were assigned a particular provincia, the scope of authority within which they exercised their command.
The territory of a people who were defeated in war might be brought under various forms of treaty, in some cases entailing complete subjection (deditio). The formal annexation of a territory created a "province" in the modern sense of an administrative unit geographically defined. Republican provinces were administered in one-year terms by the consuls and praetors who had held office the previous year and who were invested with imperium.
Rome started expanding beyond Italy during the First Punic War. The first permanent provinces to be annexed were Sicily (Sicilia) in 241 BC and Sardinia (Corsica et Sardinia) in 237 BC. Militarized expansionism kept increasing the number of these administrative provinces, until there were no longer enough qualified individuals to fill the posts. The terms of provincial governors often had to be extended for multiple years (prorogatio), and on occasion the Senate awarded imperium even to private citizens (privati), most notably Pompey the Great. Prorogation undermined the republican constitutional principle of annual elected magistracies, and the amassing of disproportionate wealth and military power by a few men through their provincial commands was a major factor in the transition from a republic to imperial autocracy.