Augustine of Hippo

(De Civ. Dei, x. 1.) By service is to be understood the honour due to God; as our version renders the Greek word ‘latria,’ wherever it occurs in Scripture, by ‘service’ (servitus), but that service which is due to men (as where the Apostle bids slaves be subject to their masters) is in Greek called ‘dulia;’ while ‘latria,’ always, or so often that we say always, is used of that worship which belongs to God.