Hamza (Arabic: الهَمْزة, al-hamzah) (ء) is a letter in the Arabic alphabet, representing the glottal stop [ʔ]. Hamza is not one of the 28 "full" letters, and owes its existence to historical inconsistencies in the standard writing system. It is derived from the Arabic letter ‘ayn. In the Phoenician and Aramaic alphabets, from which the Arabic alphabet is descended, the glottal stop was expressed by aleph (Phoenician aleph.svg), continued by alif ( Alif-individua-cropt.svg ) in the Arabic alphabet. However, alif was used to express both a glottal stop and a long vowel /aː/. To indicate that a glottal stop, and not a mere vowel, was intended, hamza was added diacritically to alif. In modern orthography, under certain circumstances, hamza may also appear on the line, as if it were a full letter, independent of an alif.