noun A writing system for Arabic, historically also employed as a numeral system, in which there is one glyph (symbol or letter) for each consonant but vowels are not specified.
noun Any writing system in which glyphs are used to represent consonants or consonantal phonemes, but not vowels.
Languages that use abjads include Arabic, Hebrew, Persian, and Urdu. Abjads differ from syllabaries (such as the Japanese hiragana) in that the vowel quality of each letter is left unspecified, and must be inferred from context and grammar.
noun The system of abjad numerals; a numeral system in which the letters of the Arabic abjad are interpreted as numerals, typically used to enumerate lists and nested lists, as well as in numerology.