hamza

noun

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