An abjad (, ; also abgad) is a writing system in which only consonants are represented, leaving vowel sounds to be inferred by the reader. This contrasts with other 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. The name abjad is based on the Arabic alphabet's first (in its original order) four letters—corresponding to a, b, j, and d—to replace the more common terms "consonantary" and "consonantal alphabet", in describing the family of scripts classified as "West Semitic". Etymology The name "abjad" is derived from pronouncing the first letters of the Arabic alphabet order, in its original order. Similar to other semitic languages such as Phoenician, Hebrew and Semitic proto-alphabets: specifically, aleph, bet, gimel, dalet. Terminology According to the formulations of Peter T. Daniels, abjads differ from alphabets in that only consonants, not vowels, are represented among the basic graphemes. Abjads differ from abugidas, another category defined by Daniels, in that in abjads, the vowel sound is implied by phonology, and where vowel marks exist for the system, such as nikkud for Hebrew and ḥarakāt for Arabic, their use is optional and not the dominant (or literate) form. Abugidas mark all vowels (other than the "inherent" vowel) with a diacritic, a minor attachment to the letter, a standalone glyph, or (in Canadian Aboriginal syllabics) by rotation of the letter. Some abugidas use a special symbol to suppress the inherent vowel so that the consonant alone can be properly represented. In a syllabary, a grapheme denotes a complete syllable, that is, either a lone vowel sound or a combination of a vowel sound with one or more consonant sounds. The antagonism of abjad versus alphabet, as it was formulated by Daniels, has been rejected by some scholars because abjad is also used as a term not only for the Arabic numeral system but (most importantly in terms of historical grammatology) also as a term for the alphabetic device (i.e., letter order) of ancient Northwest Semitic scripts in opposition to the 'south Arabian' order. This caused fatal effects on terminology in general and especially in (ancient) Semitic philology. Also, it suggests that consonantal