Mongolian Zhi and the Problem of Writing Chinese in an Alphabet

Chinese is difficult to write in any alphabet, and the difficulty is structural rather than a matter of a few awkward sounds. A Chinese syllable is a tightly constrained unit, with a limited set of initials, a limited set of finals and a tone, and the syllable rather than the individual sound is what speakers and writers treat as basic. An alphabet built for a language with different syllable shapes and no tones cannot represent that inventory efficiently: it will spell some syllables in ways no Chinese reader would accept, fail to distinguish others, and record no tone at all.

Transcription systems for Chinese have taken various routes around this, and the route the Mongolian alphabet took for a small number of frequent syllables was to supply a sign for the whole syllable rather than spell it. That is the same instinct that produced Japanese kana from Chinese characters, arrived at from the opposite direction and on a very much smaller scale. Two letters is not a syllabary, and it was never meant to be one. It is a targeted repair to an alphabet in the few places where the alphabet was failing most visibly, and it leaves every other Chinese syllable to be spelled out with whatever the alphabet can manage.