Fausset's Bible Dictionary
Philippi was one, planted with Italian colonists, transplanted from those parts of Italy which had espoused Antony's side, and which Augustus assigned therefore to his veterans. Inscriptions and coins of Augustus are still extant, with the designation "colonia" assigned to Philippi. It had the "jus Ιtalicum ", or privileges of Italian citizens. The accuracy of Acts 16:12 appears in calling Philippi kolonia (Roman), not Greek apoikia .
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Fausset, Andrew R. Entry for 'Colony'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/c/colony.html. 1949.