The Greek adjective anagkaios (ἀναγκαῖος) means "necessary," "indispensable," or "compelling." From anagkē (necessity, compulsion), it describes what is required by the nature of things or by divine purpose. The word is used of persons who are "close" or "intimate" (literally "necessary" to one), of doctrines that are essential, and of actions that are required by the situation.
Paul's use of anagkaios in Philippians 2:25 to describe Epaphroditus as "my brother, fellow worker, fellow soldier, and your messenger and minister to my need" — calling him "indispensable [anagkaion]" — reveals that Christian community involves genuine mutual necessity. We need one another. In Acts 13:46, Paul and Barnabas declare it was "necessary [anagkaion]" to speak the word of God to the Jews first — reflecting theological ordering in mission. Hebrews 9:23 speaks of heavenly things being purified with "better sacrifices than these" — these copies of heavenly things were "necessary [anagkaion]" purifications, pointing to the typological necessity of the entire sacrificial system as preparation for Christ.