Mystery

It is something hidden in Scripture that is not (yet) generally revealed (e.g., Prov 20:19). It can be negative (e.g., 2 Thess. 2:7) or positive (e.g., Ps. 25:14). Secrets are in the heart of God or man or relate to one thing (e.g. the secret of wisdom Job 11:6). God is the only one who knows all secrets (Dan. 2:47). He reveals them publicly or to individuals when he wants to. An example of something hidden in the Old Testament but revealed in the New Testament is rapture.