Appendix:Tone in Kra-Dai languages

Tone in Kra-Dai languages can be traced to various historical categories.

Background
Proto-Tai tones take on various tone values and contours in modern Tai languages. These tonal splits are determined by the following conditions:
 * 1) "Friction sounds": Aspirated onset, voiceless fricative, voiceless sonorant
 * 2) Unaspirated onset (voiceless)
 * 3) Glottalized/implosive onset (voiceless)
 * 4) Voiced onset (voiceless)

In addition, William J. Gedney developed a "tone-box" method to help determine historical tonal splits and mergers in modern Tai languages. There is a total of 20 possible slots in what is known as a "Gedney Box." (For a tutorial on Gedney boxes, see "A checklist for determining tones in Tai dialects" (1989) by William Gedney).