mystery, hidden truth

Definition:

In the Bible, the term “mystery” refers to something that we cannot know or understand unless God reveals it or explains it to us.

The New Testament states that the gospel of Christ was a mystery that was not known in past ages.
One of the specific points described as a mystery is that Jews and Gentiles would be equal in Christ.
This term could also be translated as “secret” or “hidden truth” or “previously unknown thing.”