abjad

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.

Any writing system in which glyphs are used to represent consonants or consonantal phonemes, but not vowels.

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.