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An abjad is a type of writing system where each symbol always or usually stands for a consonant, leaving the reader to supply the appropriate vowel. It is a term suggested by Peter T. Daniels to replace the common terms "consonantary", "consonantal alphabet" or "syllabary" to refer to the family of scripts called West Semitic. In popular usage, abjads often contain the word "alphabet" in their names, such as "Arabic alphabet" and "Phoenician alphabet". The name "abjad" is derived from the Arabic word for alphabet. The word "alphabet" in English has a source in Greek language in which the first two letters were "A" (alpha) and "B" (beta), hence "alphabeta". In Arabic, "A" (ʾAlif), "B" (Bāʾ), "Ǧ" (Ǧīm), "D" (Dāl) make the word "abjad" which means "alphabet". In Hebrew the first two letters are "A" (Aleph), "B" (Bet) hence "alephbet." It is also used to enumerate a list in the same manner that "a, b, c, d" (etc.) are used in the English language.
The name "abjad" (ʾabǧad أبجد) is derived from pronouncing the first letters of the Arabic alphabet in order. The ordering (ʾabǧadī ) of Arabic letters used to match that of the older Hebrew, Phoenician and Semitic alphabets; ʾ b g d (read from right to left: أ ب ج د) or أبجد.
According to the formulations of Daniels, abjads differ from alphabets in that only consonants, not vowels, are represented among the basic graphemes. Abjads differ from abugidas, another category invented by Daniels, in that in abjads, the vowel sound is implied by phonology, and where vowel marks exist for the system, such as nikkud for Hebrew and harakāt for Arabic, their use is optional and not the dominant (or literate) form. Abugidas mark the vowels (other than the "inherent" vowel) with a diacritic, a minor attachment to the letter, or a standalone glyph. Some abugidas use a special symbol to suppress the inherent vowel so that the consonant alone can be properly represented. In a syllabary, a grapheme denotes a complete syllable, that is, either a lone vowel sound or a combination of a vowel sound with one or more consonant sounds.
The antagonism of abjad versus alphabet has been rejected by other scholars because abjad is also used as a term for the Arabic numeral system. Also, it suggests as if consonantal alphabets, in opposition to for instance the Greek alphabet, were not yet true alphabets.
Values table 
The Abjad gadol (see below) values are:
All known abjads belong to the Semitic family of scripts. These scripts are thought to derive from the Proto-Sinaitic alphabet (dated to about 1500 BC), which is thought to derive from Egyptian hieroglyphs. The abjad was significantly simpler than the earlier hieroglyphs. The number of distinct glyphs was reduced tremendously at the cost of increased ambiguity.
The first abjad to gain widespread usage was the Phoenician abjad. Unlike other contemporary scripts, such as Cuneiform and Egyptian hieroglyphs, the Phoenician script consisted of only about two dozen symbols. This made the script easy to learn, and Phoenician seafaring merchants took the script wherever they went. Phoenician gave way to a number of new writing systems, including the Greek alphabet and Aramaic, a widely used abjad. The Greek alphabet evolved into the modern western alphabets, such as Latin and Cyrillic, while Aramaic became the ancestor of many modern abjads and abugidas of Asia.
Aramaic spread across Asia, reaching as far as India and becoming Brahmi, the ancestral abugida to most modern Indian and Southeast Asian scripts. In the Middle East, Aramaic gave rise to the Hebrew and Nabataean abjads, which retained many of the Aramaic letter forms. The Syriac script was a cursive variation of Aramaic. It is unclear whether the Arabic abjad was derived from Nabatean or Syriac.
Impure abjads 
"Impure" abjads have characters for some vowels, optional vowel diacritics, or both. The term "pure" abjad refers to scripts entirely lacking in vowel indicators. However, most modern abjads, such as Arabic, Hebrew, Aramaic and Avestan, are "impure" abjads, that is, they also contain symbols for some of the vowel phonemes. An example of a "pure" abjad is ancient Phoenician.
Addition of vowels 
In the 9th century BC, the Greeks adapted the Phoenician script for use in their own language. The phonetic structure of the Greek language created too many ambiguities when the vowels went unrepresented, so the script was modified. They did not need letters for the guttural sounds represented by aleph, he, heth or ayin, so these symbols were assigned vocalic values. The letters waw and yod were also used. The Greek alphabet thus became the world's first "true" alphabet.
Abugidas developed along a slightly different route. The basic consonantal symbol was considered to have an inherent "a" vowel sound. Hooks or short lines attached to various parts of the basic letter modify the vowel. In this way, the South Arabian alphabet evolved into the Ge'ez alphabet between the 5th century BC and the 5th century AD. Similarly, around the 3rd century BC, the Brāhmī script developed (from the Aramaic abjad, it has been hypothesized).
The other major family of abugidas, Canadian Aboriginal syllabics, was initially developed in the 1840s by missionary and linguist James Evans for the Cree and Ojibwe languages. Evans used features of Devanagari script and Pitman shorthand to create his initial abugida. Later in the 19th century, other missionaries adapted Evans' system to other Canadian aboriginal languages. Canadian syllabics differ from other abugidas in that the vowel is indicated by rotation of the consonantal symbol, with each vowel having a consistent orientation.
Abjads and the structure of Semitic languages 
The abjad form of writing is well-adapted to the morphological structure of the Semitic languages it was developed to write. This is because words in Semitic languages are formed from a root consisting of (usually) three consonants, the vowels being used to indicate inflectional or derived forms. For instance, according to Classical Arabic and Modern Standard Arabic, the Arabic root ذ ب ح Ḏ-B-Ḥ (to sacrifice) can be derived the forms ذَبَح ḏabaḥa (he sacrificed), ذَبَحْتَ ḏabaḥta (you (masculine singular) sacrificed), ذَبَّحَ ḏabbaḥa (he slaughtered), يُذَبِّح yuḏabbiḥ (he slaughters), and مَذْبَح maḏbaḥ (slaughterhouse). In each case, the absence of full glyphs for vowels makes the common root clearer, improving word recognition[dubious ] while reading.
Comparative chart of Abjads, extinct and extant 
|ID||Name||In use||Do the letters connect||Direction||# of letters||Country of origin||Used by||Languages||Time period (age)||Influenced by||Writing systems influenced|
|1||Syriac||yes||yes||right-left||22 consonants||Middle-East||Syrian Church||Aramaic, Syriac, Assyrian Neo-Aramaic||~ 700 BCE||Nabatean, Palmyran, Mandaic, Parthian, Pahlavi, Sogdian, Avestan and Manichean|
|2||Hebrew||yes||no||right-left||22 consonants + 5 final letters||Middle-East||Israelis, Some Jewish diaspora communities, Ancient Hebrew Tribes||Hebrew, Ladino, Bukhari, Yiddish, Judeo-Arabic||> 1100 BCE||Proto-Hebrew, Early Aramaic|
|3||Arabic||yes||yes||right-left||28||Middle-East||Over 200 million people||Arabic, Bosnian, Kashmiri, Kurdish, Kyrghyz, Malay, Persian/Farsi, Punjabi, Rajasthani, Turkish, Urdu, Uyghur, others||~ 500 CE||Nabataean Aramaic|
|4||Aramaic (Imperial)||no||no||right-left||22||Middle-East||Archaemenid, Persian, Babylonian, and Assyrian empires||Imperial Aramaic, Hebrew||~ 500 BCE||Phoenician||Late Hebrew, Nabataean, Syriac|
|5||Aramaic (Early)||no||no||right-left||22||Middle-East||Various Semitic Peoples||~ 1000-900 BCE||Phoenician||Hebrew, Imperial Aramaic.|
|6||Ancient Berber||no||no||top-bottom, right-left||22 (right-left) 25 (up-down)||North Africa||Women in Tuareg Society||Tifinagh||600 BCE||Punic, South Arabian||Tifinagh|
|7||Nabataean||no||no||right-left||22||Middle-East||Nabataean Kingdom||Nabataean||200 BCE||Aramaic||Arabic|
|8||Middle Persian, (Pahlavi)||no||no||right-left||22||Middle-East||Sassanian Empire||Pahlavi, Middle Persian||Aramaic||Psalter, Avestan|
|9||Mandaic||no||yes||right-left||24||Iraq, Iran||Ahvāz, Iran||Mandaic||~ 200 CE||Aramaic||Neo-Mandaic|
|10||Psalter||no||yes||right-left||21||Northwestern China ||Persian Script for Paper Writing||~ 400 CE ||Syriac|
|11||Phoenician||no||no||right-left, Boustrophedon||22||Byblos||Canaanites||Phoenician, Punic||~ 1000-1500 BCE||Proto- Canaanite Alphabet||Punic(variant), Greek, Etruscan, Latin, Arabic, and Hebrew|
|12||Parthian||no||no||right-left||22||Parthia (modern day equivalent of Northeastern Iran)||Parthian & Sassanian periods of Persian Empire||Parthian||~200 BCE||Aramaic|
|13||Sabaean||no||no system||right-left, boustrophedon||29||Southern Arabia (Sheba)||Southern Arabians||Sabaean||~ 500 BCE||Byblos||Ethiopic|
|14||Punic||no||no||right-left||22||Carthage (Tunisia), North Africa, Mediterranean||Punic Culture||Punic, Neo-Punic||Phoenician|
|15||Proto-Sinaitic, Proto-Canaanite||no||no||right-left||30||Egypt, Sinai, Canaan||Canaanites||Canaanite||~ 1900-1700 BCE||In conjunction with Egyptian Hieroglyphs||Phoenician, Hebrew|
|16||Ugaritic||no||yes||left-right||30||Ugarit (modern day Northern Syria)||Ugarites||Ugaritic, Hurrian||~ 1400 BCE|
|17||South Arabian||no||no||right-left, left-right (reversed letters)||29||South-Arabia (Yemen)||D'mt Kingdom||Amharic, Tigrinya, Tigre, Semitic, Chushitic, Nilo-Saharan||900 BCE||Proto-Sinaitic||Ge'ez (Ethiopia)|
|18||Sogdian||no||no (yes in later versions)||right-left, left-right(vertical)||20||parts of China (Xinjiang), Uzbekistan, Tajikistan, Pakistan||Buddhists, Manichaens||Sogdian||~ 400 CE||Syriac||Old Uyghur alphabet, Yaqnabi (Tajikistan dialect) |
|19||Samaritan||yes (700 people)||no||right-left||22||Mesopatamia or Levant (Disputed)||Samaritans (Nablus and Holon)||Samaritan Aramaic, Samaritan Hebrew||~ 100-0 BCE||Paleo-Hebrew Alphabet|
See also 
- Abjad numerals
- Gematria (Hebrew system of mystical numerology)
- Shorthand (constructed writing systems that are structurally abjads)
- "Abjads / Consonant alphabets", Omniglot.com, 2009, quote: "Abjads, or consonant alphabets, represent consonants only, or consonants plus some vowels. Full vowel indication (vocalisation) can be added, usually by means of diacritics, but this is not usually done." Accessed 22 May 2009.
- Daniels, Peter T., et al. eds. The World's Writing Systems, Oxford. (1996), p.4.
- Reinhard G. Lehmann: "27-30-22-26. How Many Letters Needs an Alphabet? The Case of Semitic", in: The idea of writing: Writing across borders / edited by Alex de Voogt and Joachim Friedrich Quack, Leiden: Brill 2012, p. 11-52, esp. p. 22-27
- , http://www.omniglot.com/writing/alphabetic.htm.
- , http://www.ancientscripts.com/berber.html.
- , Encyclopedia Iranica.
- Wright, W. (1971). A Grammar of the Arabic Language (3rd ed.). Cambridge University Press. v. 1, p. 28. ISBN 0-521-09455-0.