From didasko; an instructor (genitive case or specially) -- doctor, master, teacher.
see GREEK didasko
1. of one who is fitted to teach, or thinks himself so: Hebrews 5:12; Romans 2:20.
2. of the teachers of the Jewish religion: Luke 2:46; John 3:10; hence, the Hebrew רַב is rendered in Greek διδάσκαλος: John 1:38 ( 3. of those who by their great power as teachers drew crowds about them; a. of John the Baptist: Luke 3:12. b. of Jesus: John 1:38 ( 4. by preeminence used of Jesus by himself, as the one who showed men the way of salvation: Matthew 23:8 L T Tr WH. 5. of the apostles: ὁ διδάσκαλος τῶν ἐθνῶν, of Paul, 1 Timothy 2:7; 2 Timothy 1:11. 6. of those who in the religious assemblies of Christians undertake the work of teaching, with the special assistance of the Holy Spirit: 1 Corinthians 12:28; Ephesians 4:11; Acts 13:1, cf. James 3:1. 7. of false teachers among Christians: 2 Timothy 4:3. (Homer (h. Merc. 556), Aeschylus, others)