Ancient/Classical History/A question of Greek
What is the Greek word used for the Roman military unit named "century" which in the early empire was 80 men. Is it hekaton?
the ancient Greek word used for the Roman military unit named "century" is ἑκατοστύς (transliterated as “hekatostús”), as we read in Plutarch, Life of Romulus, chapter 8, section 6.
Note that ἑκατοστύς (transliterated as “hekatostús”), which is a feminine noun belonging to the 3rd.declension, literally means “a hundred” and has the same root of the cardinal number “hekatón” (Greek, ἑκατόν).
Also, note that ἑκατοστύς / “hekatostús” is the nominative singular used as a subject of a sentence.
Ancient Greek is in fact an inflected language with three declensions and five cases (nominative, genitive, dative, accusative, vocative) so that each noun changes ending, according to its role in a phrase.
Lastly, I have to point out that in the early years of the Roman Kingdom (753 BC-509 BC) and the Republic (508 BC- 27 BC) Roman legions are described as being organized into centuries of roughly one hundred men, whereas after the military reform of Gaius Marius in 107 BC the century consisted of 80 men distributed among 10 contubernia (of 8 men each), as the remaining number of men required for a full count of one hundred was taken up by various noncombatants attached for administrative, logistical or other purposes within the legion.
Therefore, as you can see, the centuria was composed of 80 men not in the early empire that did not exist yet in 107 BC, when there is the Roman Republic, since the Roman Empire started in 27 BC and lasted until 476 AD.
As for the “ contubernium” (literally, “tent-companionship”), it was the minimal unit in the Roman legion and its members lived in the same tent while on campaign or the same bunk room in barracks.
See the accusative ἑκατοστύας /hecatostúas in the 1st.line of Plutarch, Life of Romulus, chapter 8, section 6.
(Ῥωμύλος) πολλὴν δὲ καὶ σὺν αὑτῷ δύναμιν ἦγεσυλλελοχισμένην εἰς ἑκατοστύας: ἑκάστης δ᾽ ἀνὴρἀφηγεῖτο χόρτου καὶ ὕλης ἀγκαλίδα κοντῷ περικειμένηνἀνέχων: μανίπλα ταύτας Λατῖνοι καλοῦσιν: ἀπ᾽ ἐκείνου δὲκαὶ νῦν ἐν τοῖς στρατεύμασι τούτους μανιπλαρίους ὀνομάζουσιν.
 He (Romulus) was also leading a large force with him, divided into companies of a hundred men, each company headed by a man who bore aloft a handful of hay and shrubs tied round a pole (the Latin word for handful is ‘manipulus,’ and hence in their armies they still call the men in such companies ‘manipulares'.