an expression used by St. Paul in reference to the present and prospective privileges of Christians. (Romans 8:15,23; Galatians 4:5; Ephesians 1:5) He probably alludes to the Roman custom by which a person not having children of his own might adopt as his son one born of other parents. The relationship was to all intents and purposes the same as existed between a natural father and son. The term is used figuratively to show the close relationship to God of the Christian. (Galatians 4:4,5; Romans 8:14-17) He is received into God's family from the world, and becomes a child and heir of God.