Ghayb (the unseen) is that which is hidden from you, not from the Real (al-Ḥaqq). (Iṣṭilāḥī, 539)
The ghayb is the container of the world of shahāda (the witnessed realm). Here, the world of shahāda refers to everything, other than Allah the Exalted, that is created or uncreated, or that, after being created, is consigned to the ghayb, such as forms and accidents. The world of shahāda is the realm that is witnessed (shāhid) with respect to Allah. For this reason, we call it the world of shahāda. The Real (al-Ḥaqq) continually brings forth, piece by piece and in number, from the world of ghayb to infinity. These are individuals, genera, and species. Among these, there are things in the world that Allah returns to His ghayb and will never return eternally.
That which He will never return eternally to the ghayb is every essence (dhāt) that subsists by itself. These are, in particular, nothing other than substances (jawhar). Apart from substances, bodies and accidents such as existence and colors will be returned to the ghayb, and their likenesses will appear. Allah brings them forth from the ghayb into the world of shahāda. He is the world of ghayb and shahāda. The things in the ghayb have no quantity, because quantity requires limitation, and questions such as 'how much?' or 'how many?' are asked. This is not something that is separated from the ghayb, because it is infinite. Quantity (kamm) is related to quality (kayf), location (ayn), time, position (waḍʿ), relation (iḍāfa), accident, 'that it acts' (an yafʿala, active actions, effect), and 'that it...'