unseen / hidden realm
Masculine noun. Related: غَائِبٌ (absent), غَابَ (to be absent/hidden), غَيْبِيٌّ (relating to the unseen). Opposite: شَهَادَة (the witnessed/seen realm). عَالِمُ الْغَيْبِ = Knower of the unseen.
Belief in the ghayb (unseen) is the first quality of the God-conscious mentioned in the Quran. It encompasses God, angels, the Hereafter, and all that is beyond human perception.