noun A sign used in the written Arabic language representing a glottal stop. Hamza may appear as a stand-alone letter (ء (ʔ)) 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]) or ئ (ʔ) (over a dotless yāʾ [ى]). The exact seat of hamza is governed by an orthographic rule – the "seat of hamza rule".