- Proto-Sino-Tibetan: *s-nis (Chou, 1972); *sn̥jis (Coblin, 1986)
- Proto-Tibeto-Burman: *s-ni-s (Matisoff, STEDT); *s-nis (Benedict, 1972; Chou, 1972; LaPolla, 1987)
Apparently formed from the same root *ni(-s) as Proto-Sino-Tibetan *g/s-ni-s (“two”), showing the vestige of a quinary numeral system at some stage (probably much earlier than Proto-Sino-Tibetan), so that SEVEN was expressed as "5 + 2". However attempts to relate any part of this proto-form to the root for "five" (*l/b-ŋa) have been unsuccessful, and there is no evidence in other numerals (eg. 6&1, 8&3) to suggest the same quinary relationship.
Burmese has a prefix khu’ which as a separate morpheme means "unit, individual thing". Matisoff has argued that this component is cognate with *k(r)ut (“hand, arm”), the connection being via the five fingers used in counting. Tibetan བདུན (bdun, “seven”) is unrelated to this root and its etymology has been something of a mystery.
Preemption of the nasal root initial by prefix is seen in Chinese (if the Old Chinese reconstruction by Zhengzhang is valid) and Lolo-Burmese. Many Kuki-Chin-Naga languages have r-, ɣ- or g- as the root initial. Matisoff believes this resulted from "rhotacism", or liquefaction of the nasal.
*tjak ~ g-t(j)ik
|EIGHT||*b-r-gjat ~ b-g-rjat|
*ts(j)i(j) ~ tsjaj
- Old Chinese: 七 /*sn̥id/ (by Zhengzhang Shangfang); /*tsʰit/ (by Baxter-Sagart)
- /*Ɂnweᴬ, Ɂnwetᴰ/ (Luangthongkum, 2013)
- Sgaw: နွံ (nwi, “seven”)
- *g/s-ni-s (“two”)