Doug Ewell scripsit:

> * An alphabet has symbols for both consonants and vowels, and all are
> mandatory.

And are treated on a typographically equal footing.

> * An abjad is similar, but symbols for most vowels are optional.

Vowels are normally subordinated to consonants, appearing as diacritics
of some sort.

> * An abugida has the concept of an inherent vowel, which must be
> explicitly overridden if not present.
> * A syllabary has a separate symbol for each syllable. The shape of
> these symbols may be systematic (Ethiopic) or not (hiragana).

Ethiopic is an abugida, though encoded in Unicode as if it were a syllabary.

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