Tone Letter - Non-IPA Systems

Non-IPA Systems

Although the phrase "tone letter" generally refers to the Chao system, there are also orthographies with letters assigned to individual tones, and these may also be called tone letters.

In several systems, tone numbers are integrated into the orthography, so that they are technically letters even though they continue to be called "numbers". However, in the case of Zhuang, the 1957 Chinese orthography modified the digits to make them graphically distinct from digits used numerically; two letters were adopted from Cyrillic: ⟨з⟩ and ⟨ч⟩, replacing the similar-looking tone numbers ⟨3⟩ and ⟨4⟩. In 1982 these were replaced with Latin letters, one of which, ⟨h⟩, now pulls double-duty as a consonant letter for /h/ and as a tone letter for mid tone.

The Hmong Romanized Popular Alphabet was devised in the early 1950s with Latin tone letters. Two of the 'tones' are more accurately called register, as tone is not their distinguishing feature. Several of the letters pull double duty representing consonants.

(The low-rising creaky register is a phrase-final allophone of the low-falling register.)

And a unified Miao alphabet used in China applies a different scheme:

The Uralic Phonetic Alphabet has marks resembling half brackets that indicate the beginning and end of high and low tone: mid tone ˹high tone˺ ˻low tone˼.