Strong’s Greek
G141 — hairetikos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
αἱρετικός
hairetikos — pronounced hahee-ret-ee-kos'
from the same as 140; a schismatic:--heretic (the Greek word itself). see GREEK for 140
1 occurrence in the KJV.
Titus 3:10
A man that is an heretick after the first and second admonition reject;