Ẓāʾ  ', or ' (), is one of the six letters the Arabic alphabet added to the twenty-two inherited from the Phoenician alphabet (the others being , , , , ). In Classical Arabic, it represents a velarized voiced dental fricative , and in Modern Standard Arabic, it can also be a pharyngealized, voiced dental fricative or voiced alveolar fricative . In name and shape, it is a variant of . Its numerical value is 900 (see Abjad numerals).  "" does not change its shape depending on its position in the word:  In Classical Arabic, it represents a velarized voiced dental fricative , and in Modern Standard Arabic, it can also be a pharyngealized, voiced dental fricative or voiced alveolar fricative . In most Arabic vernaculars "ẓāʾ" and "ḍād" have been merged quite early. The outcome depends on the dialect. In those varieties (such as Egyptian, Levantine and Hejazi), where the dental fricatives , are merged with the dental stops , , "ẓāʾ" is pronounced or depending on the word; e.g. is pronounced but is pronounced , In loanwords from Classical Arabic "ẓāʾ" is often , e.g. Egyptian "ʿaẓīm" (< Classical "ʿaḏ̣īm") "great". In the varieties (such as Bedouin and Iraqi), where the dental fricatives are preserved, both "ḍād" and "ẓāʾ" are pronounced . However, there are dialects in South Arabia and in Mauritania where both the letters are kept different but not consistently. A "de-emphaticized" pronunciation of both letters in the form of the plain entered into other non-Arabic languages such as Persian, Urdu, Turkish. However, there do exist Arabic borrowings into Ibero-Romance languages as well as Hausa and Malay, where "ḍād" and "ẓāʾ" are differentiated.   is the rarest phoneme of the Arabic language. Out of 2,967 triliteral roots listed by Hans Wehr in his 1952 dictionary, only 42 (1.4%) contain . In some reconstructions of Proto-Semitic phonology, there is an emphatic interdental fricative, ( or ), featuring as the direct ancestor of Arabic , while it merged with in most other Semitic languages, although the South Arabian alphabet retained a symbol for .