The Greek adjective dikaios means righteous, just, or upright — describing a person or thing that conforms to God's standard of right. It is the adjectival form of the dik- word family that includes dikaiosyne (righteousness) and dikaioo (justify). A dikaios person is one who is in right standing before God and acts in accordance with that standing.
Dikaios carries both a forensic dimension (declared righteous before God's court) and an ethical dimension (living righteously). In the New Testament, only God is perfectly dikaios (Romans 3:26). Through Christ's atoning work, sinners are declared dikaios by faith (Romans 3:24–26). But justification is never merely legal — it transforms, producing genuine righteousness of life. Joseph (Matthew 1:19), Simeon (Luke 2:25), and Cornelius (Acts 10:22) are called dikaios as models of this transformation.