The Greek adjective hairetikos (αἱρετικός) describes a person who is divisive, factious, or heretical — one who 'chooses' their own path over the received apostolic teaching, creating party divisions in the church. It appears only once in the New Testament, in Titus 3:10, where Paul instructs Titus on how to handle such a person.
The word comes from haireō (to choose) — the heretic is literally a 'chooser,' someone who picks and selects doctrines according to personal preference rather than submitting to the whole counsel of God's Word. Heresy began as a neutral term for a 'school of thought' but took on negative connotations as it described those whose chosen views fractured the community.
Paul's instruction in Titus 3:10 is remarkably brief and decisive: warn a divisive person twice, and then have nothing to do with them. This is not harsh — it is pastoral clarity. The church's unity and doctrinal integrity are not optional extras; they are essential to the community's witness and health.
The broader NT teaching on heresy/division (Romans 16:17, 1 Corinthians 1:10–13, Galatians 1:6–9, 2 Peter 2) consistently treats doctrinal and relational fractures as serious threats — not minor disagreements. The standard is not uniformity of opinion on every topic, but submission to the apostolic Gospel. Where that core is abandoned and a divisive party is formed, the church must act. John's letters are similarly clear: test the spirits; some who teach falsely have gone out from the community (1 John 2:19).