Italic languages

The combined Greek population of the western colonies in 500 BC was probably between 1 and 1.5 million.

That's a Greek-speaking civilization, equivalent in size to roughly half of mainland Greece, planted in territory that had been inhabited a generation or two earlier by Italic peoples.

These cities tended to assimilate the native populations of the surrounding lands quite quickly, which swelled the number of people considered Greeks even further.

After all, it's important to remember that to be a Greek was, largely speaking, to not be a barbarian.

The Latin League, including Rome itself, may have totaled three to four hundred thousand at this point.

Rome was still a minor city of perhaps 30,000, only a few years removed from the expulsion of its last king, and still well within the orbit of its larger Etruscan neighbors.

The Samnites, Oscans, and other inland Italic peoples added perhaps another million.

The total Italic-speaking population came out to somewhere around 3 million, though large pockets of southern Italy had already been culturally Hellenized.