Arabic abjad, is the Arabic script as it is codified for writing Arabic. It is written from right to left in a cursive style and includes 28 letters. Most letters have contextual letterforms.
The Arabic alphabet is considered an abjad, meaning it only uses consonants, but it is now considered an "impure abjad". As with other impure abjads, such as the Hebrew alphabet, scribes later devised means of indicating vowel sounds by separate vowel diacritics.
The Arabic alphabet is the third most used writing system in the world, after the Latin alphabet and Chinese characters.
It is the most common script to write for the Arabic language, and it is also the most common script used to write for some other languages with large numbers of Muslim speakers such as Persian and Urdu, and it is one of the variant scripts used to write in other languages such as Punjabi, Malay, and Sundanese. All of the aforementioned languages added some letters to represent phonemes absent from Arabic, but present in the aforementioned languages. It is also used as the base to write the Uighur Arabic alphabet, which uses many of the same letters as the Arabic alphabet, but differs in the fact that the Uighur Arabic alphabet added mandatory vowel letters, as opposed to vowel diacritics that are usually optional and/or omitted.
It was also once used by Muslim speakers of several other languages in Eastern Europe and Central Asia such as Turkish, Kazakh, and Bosnian, but speakers of the aforementioned languages later adopted a different script such as the Latin alphabet or Cyrillic due to a variety of reasons such as secularization of the government, like in the case of Turkish, or imposition of the national government on minority languages, such as with the case of Kazakh when Kazakhstan was a part of the Soviet Union.