The Arabic alphabet is consider an abjad, which means an alphabet that only contains consonants (though there are the weak consonants that function as long-vowels). In normal use, this leaves the reader to use their knowledge of Arabic word forms to infer the correct meaning.

In educational materials and religious texts though, it is important to know the exact vowel pronunciations. For this, Arabic uses a system called harakat. It is a set of diacritical marks that specify vowel sounds. Harakat are not used in general publications like newspapers, novels, instructions manuals, or streets signs.

Most harakat specify short-vowel sounds like /a/, /u/, and /i/, but there are two special cases that do not: