6I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel: 7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ. — Galatians 1:6,7 KJV
euangelion n def good news
Originally a reward for good tidings; later the word stood for the good news itself. In the New Testament it was the good news of the Kingdom of God and of salvation through Christ, to be received by faith, on the basis of Jesus’ death, burial, resurrection, and ascension.