Abjad
An abjad (/ˈæbdʒæd/ ⓘ or abgad) is a writing system in which only consonants are represented, leaving the vowel sounds to be inferred by the reader. This contrasts with alphabets, which provide graphemes for both consonants and vowels. The term was introduced in 1990 by Peter T. Daniels. Other terms for the same concept include partial phonemic script, segmentally linear defective phonographic script, consonantary, consonant writing, and consonantal alphabet.
Impure abjads represent vowels with either optional diacritics, a limited number of distinct vowel glyphs, or both.