Terminology
According to the formulations of Daniels, abjads differ from alphabets in that only consonants, not vowels, are represented among the basic graphemes. Abjads differ from abugidas, another category invented 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 harakāt for Arabic, their use is optional and not the dominant (or literate) form. Abugidas always mark the vowels (other than the "inherent" vowel) with a diacritic, a minor attachment to the letter, or a standalone glyph. 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 has been rejected by other scholars because abjad is also used as a term for the Arabic numeral system. Also, it suggests as if consonantal alphabets, in opposition to for instance the Greek alphabet, were not yet true alphabets.
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