Back to the original topic...
Wikipedia has an unfair amount of influence over what audiences learn, despite its notorious unreliability. The articles are often written in obtuse and confusing manner. I have seen academic papers that are easier to read. Omniglot is superior in this regard, since it explains what the five commonly accepted writing systems are in simple English.
These are (with various synonyms):
- Abjads, or consonant alphabets*
- Alphabets, or phonemic alphabets*
- Syllabic alphabets*, alphasyllabaries or abugidas
- Semanto-phonetic writing systems
(*)While typically treated as separate writing systems, the three types of alphabets share common descent from Egyptian Hieratic and carry a similar functional load. Indeed, phonemic and syllabic alphabets are functionally identical. Henceforth, my usage of the word "alphabet" without a qualifier refers collectively to all three.
Some writing systems do not fit neatly into these categories. For example, academic Hye K. Pae labeled hangul an "alphabetic syllabary" and a "syllabic alphabet". Heidi Swank streamlines the definition of alphasyllabary to put an end to arguments regarding corner cases. Some scripts may sit somewhere between a syllabary and an alphabet, and Wikipedia lumps these into a nebulous "semi-syllabary" category regardless of origin and development.
Most such corner cases may be easily folded into another category by taking into account their origin and development:
- Old Persian and Bamum, for example, are defective syllabaries. They stopped making new graphemes part way through and filled the gaps by using digraphs. I do not consider this a distinct writing system.
- Pahawh Hmong, using Swank's definition, is an alphasyllabary which uses vowels as the independent phone rather than consonants. It is not a syllabary because none of its graphemes represent the body or rime of a syllable.
- Meroitic, according to one of the two common interpretations, is a phonemic alphabet with an implicit vowel following consonants. This does not make it an alphasyllabary.
- Zhuyin and Khom divides graphemes into onsets and rimes, but this is just the reverse of syllabaries which have graphemes for bodies and codas. If we want to be consistent, these would be labeled syllabary.
The Paleohispanic scripts are the only ones which seem to qualify as a distinct writing system, or more accurately a mix of alphabetic and syllabic graphemes. Unlike Old Persian or Bamum, this arrangement is not random: only plosives occur as syllabograms. This is believed to be because the Paleohispanic languages did not allow plosives to begin consonant clusters.
What I find fascinating is that alphabets and syllabaries arise independently from semanto-phonetic systems, but there are only a couple cases of an alphabet or syllabary transitioning into the other. Of course I might have missed something, but I do not recall any such transition being complete.
Some conscripts on Omniglot defy conventions found in real writing systems. Two such conscripts are Aziana and Chumauni. Aziana has graphemes for vowels: consonants are always appended to vowels, except special coda consonants, but the vowel grapheme is always rotated 90° when used in a CV syllable; if such a consonant appears without a following vowel, a null vowel diacritic is appended. In Chumauni, graphemes for vowels and consonants are always superimposed in CV syllables; a lone vowel or consonant is always appended with a null consonant or vowel, respectively.
Just when I think things cannot get more interesting, the internet always manages to surprise me.