The Arabic alphabet consists of 28 letters, all of which are consonants. Three of the letters can be, however, substitute as long vowels. It is the second most common alphabet in the world. It is descended from the Nabataean Aramaic script. This script was in use beginning in the 4th century AD. The earliest surviving inscription is dated 512 AD.
There two different styles for writing the Arabic alphabet: the Küfic and naskhï. Küfic, the earlier of the two, was written with thick, squat and unslanted strokes. Küfic script was particularly suited for inscriptions written or carved into stone or on walls. The nashkï writing style, which appeared in the 11th century, was customarily written on papyrus and eventually replaced Küfic to evolve into modern Arabic writing after it underwent numerous changes.
In the 7th century, the Aramaic alphabet was customized to Arabic. The Aramaic language does not have as many consonants as Arabic, so new characters were introduced. As well, diacritic marks were added to indicate short vowels. These accent marks were generally only included in the Qur'an to ensure correct pronunciation. Today they are used in religious texts, classical poetry and books teaching the Arabic language. In some instances, they are used purely for decorative purposes.
The Arabic language is written from right to left in horizontal lines; however, numerals are transcribed left to right.
Each individual character of the Arabic alphabet changes form depending on its position within a word. There are four different shapes of characters based on whether the letter is present at the beginning of a word, in the middle of a word, at the end of the word or single letters. Singular letters and letters written at the end of words typically have a bold flourish, while letters at the beginning and in the middle of words are abbreviated forms.
Arabic script dictates which letters may join to the preceding and following letters. Six letters are only permitted to be joined to the preceding letter. Otherwise, letters always are adjoining.
The Arabic alphabet has been adopted to write many other languages, including Kurdish, Pashto, Persian, Punjabi and Turkish.
Arabic has many sound values not commonly used in European languages. It has guttural and hissing sounds.
Arabic forms words by adding vowels to consonants with diacritic marks. An acute accent (´) above or below a letter indicates a short vowel. Long vowels are added by using the acute accent, and the characters known as alif for "a", wa:w for "u" and ya: for "i".
Other diacritics used in the Arabic language include the hamza, shaped like a "c", which designates a glottal stop (a way of indicating a voiceless pause is required), the suku:n, shaped like a circle, on top of a letter to indicate there is no vowel and the shadda, shaped like a "w", to double a consonant.
A group of consonants in excess of two does not exist in Arabic words. Arabic words commence with a consonant followed by a vowel. Long vowels are generally not followed by more than one consonant.