Muqattaʿat

The mysterious letters (muqaṭṭaʿāt, Arabic: حُرُوف مُقَطَّعَات ḥurūf muqaṭṭaʿāt, "disjoined letters" or "disconnected letters") are combinations of between one and five Arabic letters that appear at the beginning of 29 out of the 114 chapters (surahs) of the Quran just after the Bismillāh Islamic phrase. The letters are also known as fawātiḥ (فَوَاتِح) or "openers" as they form the opening verse of their respective surahs.

Four (or five) chapters are named for their muqaṭṭaʿāt: Ṭā-Hā, Yā-Sīn, Ṣād, Qāf, and sometimes Nūn.

The original significance of the letters is unknown. Tafsir (exegesis) has interpreted them as abbreviations for either names or qualities of God or for the names or content of the respective surahs. The general belief of most Muslims is that their meaning is known only to God. The Arabic word for "Gayab" is غَائِب (ghāʔib), meaning "absent" or "missing". In the context of Al-Ghayb (الغيب), it refers to the unseen, hidden, or concealed. It can also be used to describe something that is lost or vanished, divine, which is known as "Gayb". Some people refer to it as angelic numerology or to the very significant, divine hidden meaning of the letters. However, this is one of the profound secrets of the Quranic divine openings.