Strong’s Greek
G646 — apostasia
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ἀποστασία
apostasia — pronounced ap-os-tas-ee'-ah
feminine of the same as 647; defection from truth (properly, the state) ("apostasy"):--falling away, forsake. see GREEK for 647
2 occurrences in the KJV.
Acts 21:21
And they are informed of thee, that thou teachest all the Jews which are among the Gentiles to forsake Moses, saying that they ought not to circumcise their children, neither to walk after the customs.
2 Thessalonians 2:3
Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;