Tone letter

Register (level) tone
˥ ˦ ˧ ˨ ˩
IPA number	519–523
Entity (decimal)	˥–˩
Encoding
Unicode (hex)	U+02E5–U+02E9

Contour tone
˥˧ ˦˨ ˧˩ ˥˩ ˩˧ ˨˦ ˧˥ ˩˩˧ ˧˥˦ ˦˩˨ ˨˩˧
The contour-tone letters are composed as sequences: ˥ ˧ → ˥˧, ˨ ˩ ˧ → ˨˩˧

Tone letters are letters that represent the tones of a language, most commonly in languages with contour tones.

A series of iconic tone letters based on a musical staff was invented by Yuen Ren Chao and adopted into the International Phonetic Alphabet.

Combinations of these tone letters are schematics of the pitch contour of a tone, mapping the pitch in the letter space and ending in a vertical bar. For example, [ma˨˩˦] represents the mid-dipping pitch contour of the Chinese word for horse, 马 mǎ. Single tone letters differentiate up to five pitch levels: ˥ 'extra high' or 'top', ˦ 'high', ˧ 'mid', ˨ 'low', and ˩ 'extra low' or 'bottom'. No language is known to depend on more than five levels of pitch.

These letters are most commonly written at the end of a syllable. For example, Standard Chinese has the following four tones in syllables spoken in isolation:

However, they are sometimes written before the syllable, in accordance with writing stress and downstep before the syllable. For example, the following passage transcribes the prosody of European Portuguese using tone letters alongside stress, upstep, and downstep in the same position before the syllable:

Diacritics may also be used to transcribe tone in the IPA. For example, tone 3 in Mandarin is a low tone between other syllables, and can be represented as such phonemically. The four Mandarin tones can therefore also be transcribed [má, mǎ, mà, mâ]. (Note that these conflict with the convention of Pinyin, and so in this case IPA diacritics may be confusing.)

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