The Greek doulos (G1401) means a slave or bond-servant — one who belongs entirely to another. In the New Testament this term is radically redeemed, becoming the highest description of relationship to God and the greatest title of honor for apostles.
In the Greco-Roman world, doulos carried the full weight of servitude and ownership. Yet Paul opens his most systematic letter — Romans — by calling himself 'a doulos of Christ Jesus.' This is not degradation but the highest freedom: to be owned by the King of the universe is the most honored position in existence. Jesus himself took the form of a doulos (Philippians 2:7), and in so doing transformed the word forever — servanthood is now the path to greatness in the kingdom of God.