The Arabic alphabet was first developed by around 500 AD. It consists of 28 letters, all of which are consonants, and is written from right to left. Whether a letter is in initial, medial, or final position in a word determines the shape of the letter. Vowels are optionally indicated by diacritical marks above or below consonants. There are 6 vowel sounds in Arabic — long a, i, u and short a, i, u. Among the consonants are several guttural sounds that make Arabic sound quite different from European languages.
After the Roman alphabet, the Arabic alphabet is the second-most widely used writing system in the world. Besides Arabic, it is used for writing Persian, Urdo, Pashto, Malay, and a number of other languages primarily used in Asian countries.