A sign (ء(ʔ) - a stand-alone hamza) used in the writtenArabiclanguage representing a glottal stop. Hamza may appear as a stand-alone letter or most commonly diacritically over or under other letters, e.g. أ(ʔ) (over an alif - ا), إ(ʔ) (under an alif), ؤ(ʔ) (over a wāw - و(w)) or ئ(ʔ) (over a dotless yāʾ - ى). The exact seat of hamza is governed by an orthographic rule - "seat of hamza rule".