Here is possibly the clearest and most concise scriptural definition of apostasy-receiving knowledge of the truth, that is, the gospel, but willfully remaining in sin. An apostate has seen and heard the truth—he knows it well—but he willfully rejects it.
Apostasy has two major characteristics: knowledge of the truth of the gospel and willful rejection of it.
Every apostate is an unbeliever, but not every unbeliever is an apostate. Many people have never had the opportunity to hear the gospel, even in part. They are sinful and, of course, do not believe in Christ, because they have never heard of Him or of His claims. An apostate, however, is well acquainted with the gospel. He knows more than enough to be saved...