Dieses Zeichen ist ein Nonspacing Mark und erbt seine Schrift-Eigenschaft vom vorhergehenden Zeichen. Es wird auch in den Schriften Arabisch, Syriac verwendet.
Das Zeichen ist keine Zusammensetzung. Es hat keine zugewiesene Weite in ostasiatischen Texten. In bidirektionalem Text handelt es als Nonspacing Mark. Bei einem Richtungswechsel wird es nicht gespiegelt. U+0654 verbietet einen Zeilenumbruch vor sich. Der Buchstabe kann mit 5 anderen Zeichen verwechselt werden.
Die Wikipedia hat die folgende Information zu diesem Codepunkt:
The hamza (Arabic: هَمْزَةhamza) (ء) is an Arabic script character that, in the Arabic alphabet, denotes a glottal stop and, in non-Arabic languages, indicates a diphthong, vowel, or other features, depending on the language. Derived from the letter ʿAyn (ع), the hamza is written in medial and final positions as an unlinked letter or placed above or under a carrier character. Despite its common usage as a letter in Modern Standard Arabic, it is generally not considered to be one of its letters, although some argue that it should be considered a letter.
The hamza is often romanized as a typewriter apostophe ('), a modifier letter apostrophe (ʼ), a modifier letter right half ring (ʾ), or as the International Phonetic Alphabet symbol ʔ. In Arabizi, it is either written as "2" or not written at all.
In the Phoenician, Hebrew and Aramaic alphabets, from which the Arabic alphabet is descended, the glottal stop was expressed by alif (𐤀), continued by Alif (ا) in the Arabic alphabet. However, Alif was used to express both a glottal stop and a long vowel /aː/. In order to indicate that a glottal stop is used and not a mere vowel, it was added to Alif diacritically. In modern orthography, hamza may also appear on the line, under certain circumstances as though it were a full letter, independent of an alif.