Abjads

The first type of alphabet that was developed was the abjad. An abjad is an alphabetic writing system where there is one symbol per consonant. Abjads differ from regular alphabets in that they only have characters for consonantal sounds. Vowels are not usually marked in abjad.

All known abjads (except maybe Tifinagh) belong to the Semitic family of scripts, and derive from the original Northern Linear Abjad. The reason for this is that Semitic languages and the related Berber languages have a morphemic structure which makes the denotation of vowels redundant in most cases.

Some abjads (like Arabic and Hebrew) have markings for vowels as well, but only use them in special contexts, such as for teaching. Many scripts derived from abjads have been extended with vowel symbols to become full alphabets, the most famous case being the derivation of the Greek alphabet from the Phoenician abjad. This has mostly happened when the script was adapted to a non-Semitic language.

The term abjad takes its name from the old order of the Arabic alphabet's consonants Alif, Bá, Jim, Dál, though the word may have earlier roots in Phoenician or Ugaritic.

Abjad is still the word for alphabet in Arabic, Malay, and Indonesian.