Due to the influence of Islam, the Arabic alphabet is one of the most widespread writing systems in the world, found in large parts of Africa and Western and Central Asia, as well as in ethnic communities in East Asia, Europe, and the Americas. While originally used to write the Arabic language, the Arabic alphabet has been adopted by other groups to write their own languages, such as Persian, Pashto, Urdu, and more.
Although Arabic inscriptions are most common after the birth of Islam (7th century CE), the origin of the Arabic alphabet lies deeper in time. The Nabataeans, which established a kingdom in what is modern-day Jordan from the 2nd century BCE, were Arabs. They wrote with a highly cursive Aramaic-derived alphabet that would eventually evolve into the Arabic alphabet. The Nabataeans endured until the year 106 CE, when they were conquered by the Romans, but Nabataean inscriptions continue to appear until the 4th century CE, coinciding with the first inscriptions in the Arabic alphabet (which is also found in Jordan).
Generally speaking, there are two variants to the Arabic alphabet: Kufic and Naskhi. The Kufic script is angular, which was most likely a product of inscribing on hard surfaces such as wood or stone, while the Naskhi script is much more cursive. The Kufic script appears to be the older of the scripts, as it was common in the early history of Islam, and used for the earliest copies of the Qu'ran. The following is an example of the Kufic script. This is part of a commemorative tablet dating to the 11th century CE and found in Toledo, Spain (which was controlled by Arabs at that time).
By the 11th century CE, the Naskhi script appeared and gradually replaced the Kufic script as the most popular script for copying the Qu'ran as well as secular and personal writings. It is from the Naskhi script that modern Arabic script style developed.
The following is the Arabic alphabet in the Naskhi script.
One interesting feature of Arabic is the multiple forms of a single letter. Depending on where in a word a letter appears, it could appear as an initial form (beginning of word), final form (end of word), or medial form (anywhere else). In addition, if the word has only one letter, than the isolated form is used.
Like other Proto-Sinaitic-derived scripts, Arabic doesn't have letters for vowels. However, there is a system to marking vowels. Short vowels are represented by diacritics above or below a letter (see below). Long vowels are represented by using the short-vowel diacritics plus the letters alif, wa:w, ya: to represent the sounds [a:], [u:], and [i:], respectively. (Note that in the following example, the big dot is not a diacritic but is part of the letter nun)
In addition to the vowel markers, Arabic also has several other diacritics. The hamza, which looks like C, denotes the glottal stop (the letter alif used to represent the glottal stop, but has become more of a placeholder for vowel-initial words). The hamza requires a "seat" letter (such as alif but also wa:w and ya:) to anchor onto. Another diacritic is the suku:n, which looks like a circle and is placed on top of a letter to denote the absense of any vowel. Finally, the diacritic shadda, which resembles W, represents the doubling of a consonant.
And finally, Arabic uses a 10-base positional number system: