What is an abjad script?

An abjad script is a writing system in which each symbol represents a consonant, leaving the reader to infer the appropriate vowel sounds. Abjads are common in many Semitic languages, such as Arabic and Hebrew. Vowels are either not represented at all or indicated with diacritical marks. This characteristic distinguishes abjads from alphabets, where both consonants and vowels are typically represented by distinct symbols.