Tone number

A tone number is a numeral used in a notational system for marking the tones of a language. The number is usually placed after the romanized syllable. Notice that a number may have very different meanings in different contexts since the systems may have developed independently.

Chinese language study
In the Chinese tradition, numbers are assigned to various tones. For example, Standard Mandarin has four tones and the numbers 1, 2, 3, and 4 are assigned to them. Although those tones have names, which are more meaningful in the comparative study among geographical and chronological language varieties, most people refer to tones by number: "the first tone", "the second tone", and so on.

Tone numbers are also assigned for other spoken Chinese varieties according to various traditions, which may be unrelated to each other. The numbers are also unrelated to the relative pitch or the tones. That can be illustrated by comparing the tone charts of Standard Mandarin, Standard Cantonese and Taiwanese.

Note: Tone sandhi rules and the unstressed syllable of Standard Mandarin are not listed here for simplicity.

Although tone numbers are quite useless in comparative studies, they are useful within the context of a specified dialect, since they are easy references. For example, we may see these descriptions:
 * In Standard Mandarin, the numeral 1, originally in tone 1, is pronounced in tone 4 if followed by a classifier in tone 1, 2, or 3. It is pronounced in tone 2 if the classifier is in tone 4.
 * The Standard Cantonese tones 7, 8, and 9 have the same tone contour as tones 1, 3, and 6 respectively.
 * In Taiwanese tone sandhi, tone 1 is pronounced as tone 7 if followed by other syllables in multisyllabic words.

Some romanization schemes, like Jyutping, use tone numbers. Even for Pinyin, tone numbers are used instead when diacritics are not available, as in basic ASCII text.

Other languages
Tone numbers are also used in the study of other tonal languages. Sometimes, 1 may mean high pitch and 5 may mean low pitch. We have to refer to the individual traditions to get the correct meanings.