The Arabic alphabet contains 28 basic letters with a variety of special characters and vowel markers. It is written in a cursive style, and unlike the Latin alphabet, is read right to left.
Linguists refer to the Arabic alphabet as an abjad, a writing system which contains no vowels. While originally this was true, it now has two different forms of marking vowels. Long-vowels are represented with weak consonants ( ا (alif), و (waaw), and ي (yaa)), and optional diacritical marks, called harakat, provide short-vowel sounds and further pronunciation cues.
Arabic letter forms do not have an upper or lower case such in the Latin alphabet. However, because Arabic is written in a connected cursive style, each letter has different forms given its position in the word. The four forms a letter can have are: isolated, initial, medial and final form. The exception to this are ا (alif), د (daal), ذ (dhaal), ر (raa), ز (zayn / zaa), and و (waaw) which are called selfish letters because they do not connect with others. These letters use the isolated or final form depending on their position.
The cursive style of Arabic has also allowed for the rise of ligatures, two separate letters written in a conjoined form, and other modified letters.
Arabic is not the only language that uses the Arabic abjad. Other languages such as Persian, Ottoman (pre-regularization Turkish), Sindhi, Urdu, Malay and Pashto do as well, though with slight alterations.