What does octōnus mean in Latin?

octōnus, a numeral, means “eight each; eight at a time; eight, eighth, eightfold”.

How do you pronounce octōnus?

In classical Latin, [ɔkˈtoː.nʊs]; in ecclesiastical (church) Latin, [okˈtɔː.nus].

numeralfirst/second-declension numeral

octōnus (feminine octōna, neuter octōnum)

Classical[ɔkˈtoː.nʊs]Ecclesiastical[okˈtɔː.nus]

in pluralnumeraleight each; eight at a time
Huius generis octoni ordines ducti ternos inter se pedes distabant.Rows by eights of this kind were dug, they stood apart three feet between them.c. 52 BCE, Julius Caesar, Commentarii de bello Gallico 7.73
Pseudodipteros autem sic collocatur, ut in fronte et postico sint columnae octonae, in lateribus cum angularibus quindenae.The Pseudodipteros, however, is thus assembled so that there are eight columns each in front and rear, fifteen each on the sides including the corner ones.c. 15 BCE, Vitruvius, De architectura 3.1
numeralpoeticeight, eighth, eightfold
Laeta bis octono tibi iam sub consule pubes / cingebat teneras, Glaucia adulte, genas.Already until thy twice eighth year, glad youth was wreathing thy tender cheeks, grown Glaucias.c. 310 CE – c. 394 CE, Ausonius, Epigrams 62 De Glaucia inmatura Morte praevento.1

singular
form	masculine	feminine	neuter
nominative	octōnus	octōna	octōnum
genitive	octōnī	octōnae	octōnī
dative	octōnō	octōnae	octōnō
accusative	octōnum	octōnam	octōnum
ablative	octōnō	octōnā	octōnō
vocative	octōne	octōna	octōnum

plural
form	masculine	feminine	neuter
nominative	octōnī	octōnae	octōna
genitive	octōnum octōnōrum	octōnum octōnārum	octōnum octōnōrum
dative	octōnīs	octōnīs	octōnīs
accusative	octōnōs	octōnās	octōna
ablative	octōnīs	octōnīs	octōnīs
vocative	octōnī	octōnae	octōna

octōnus, v. octoni

I. fin.

From earlier *oktōsnos, equivalent to octō + -nus.