Centuria (Latin: centuria - hundred; from centum - hundred) was a military combat unit (formation) of the Roman legion. The commander of a centuria was called a centurion.
In the roman legion, there were initially 60 centuriae, and during the time of the Empire, there were 59 centuriae. According to the majority of historians, originally a centuria did indeed consist of 100 individuals, which is roughly equivalent to a modern army company, although there are differing views on this matter. Some authors refer to the fact that during the time of the Roman Kingdom, considering the Servian reforms, there simply would not have been enough soldiers for 193 centuriae. As a result, the size of the centuria turned out to be smaller than intended. It is presumed that prior to Gaius Marius' reforms, a centuria may have had around 60 individuals, and after the reforms, the number could have reached 100. Centuriae were divided into contubernia, consisting of 10 individuals. Two centuriae formed a manipulus, and several manipuli formed a cohort. The centuria itself, in most cases, did not act as an independent tactical unit in battle. The centuriae of the first cohort of a legion were twice the size of the centuriae in the other cohorts.
Additionally, the term "centuria" was used to refer to the electoral groups of Romans. They were introduced by the Roman king Servius Tullius (6th century BCE), who divided all Roman citizens into five property classes (excluding those who did not meet the census requirements - the so-called proletarii). Each of these classes was required to provide a specified number of centuriae, armed in a certain manner, for military service. It is known that as a result of the reform, 193 centuriae were assembled. As a result, every Roman citizen upon reaching adulthood was assigned to one of the centuriae of their class. These centuriae also voted in one of the types of popular assembly - the centuriate comitia. Later, this division became obsolete and was abolished, but nonetheless, the centuriate comitia continued to be held.