ἀδελφός

a brother

Definition

The Greek word ἀδελφός primarily means a biological brother, as seen in lists of Jesus's family (Matthew 13:55) or the calling of Peter and Andrew (Matthew 4:18). In the New Testament, it expands to signify a fellow member of the covenant community, used for fellow Jews (Acts 2:29, Romans 9:3) and, most distinctively, for a fellow Christian, denoting spiritual kinship in Christ (Matthew 23:8, Romans 8:29). This familial language is central to describing the church, where believers are adopted as brothers and sisters of Jesus and of one another.

Biblical Usage

ἀδελφός is used extensively throughout the New Testament, with high frequency in the Gospels, Acts, and the Pauline epistles. It commonly appears in ethical instructions on community life (e.g., Matthew 18:15, 1 Thessalonians 4:6) and in greetings to churches (e.g., Philippians 4:1). A key pattern is its use to define the new, spiritual family formed around Jesus, often contrasting with biological ties (Mark 3:33-35).

Etymology

Derived from the prefix ἀ- (a-, denoting 'from the same') and δελφύς (delphys, 'womb'). Thus, its core meaning is 'from the same womb,' indicating a close, physical sibling relationship. This biological foundation powerfully informs its metaphorical extension to describe spiritual kinship in the New Testament.

Semantic Range

This word is theologically rich, foundational to the doctrine of the church as the family of God. It underscores the believer's adoption into God's household (Romans 8:15-17, Galatians 4:5-7) and the resulting unity and mutual obligation among Christians (1 John 4:20-21). Understanding this Greek term enriches reading by revealing how the New Testament redefines family around loyalty to Christ and love within the believing community.

In the ancient Mediterranean world, the brother relationship implied strong loyalty, shared identity, and mutual responsibility within the extended family or clan. The New Testament's application of this term to the Christian community would have conveyed a powerful sense of belonging, obligation, and intimate connection that surpassed ordinary social associations.

συγγενής (syngenēs, G4773) — a relative or kinsman, a broader term for family connection. πλησίον (plēsion, G4139) — a neighbor, focusing on proximity and ethical duty rather than familial bond. φίλος (philos, G5384) — a friend, emphasizing affection and choice rather than inherent kinship.

Word Details

Scripture References