The Greek adjective basileios means royal, kingly, belonging to the king. It derives from basileus (king) and can refer to royal persons, royal residences, royal prerogatives, or that which is befitting a king. In 1 Peter 2:9 it appears as part of one of the most profound descriptions of the Church.
When Peter declares believers to be a "royal priesthood" (basileion hierateuma in 1 Peter 2:9), he is drawing on Exodus 19:6 where God promised Israel the same identity. The significance is staggering: every believer in Christ simultaneously holds royal status and priestly function. The royal dimension means direct access to the King; the priestly dimension means standing between God and the world in intercession and proclamation. Christ's kingdom is not a future dream but a present reality, and those united to the King bear His royal character now.