From Proto-Tai *siːᴮ (“four”), from Middle Chinese 四 (MC sijH, “four”), from Proto-Sino-Tibetan *b-ləj (“four”). Cognate with Northern Thai ᩈᩦ᩵, Lao ສີ່ (sī), Lü ᦉᦲᧈ (ṡii¹), Tai Dam ꪎꪲ꪿, Shan သီႇ (sìi), Tai Nüa ᥔᥤᥱ (sǐ), Thai สี่ (sìi), Bouyei sis, Zhuang seiq.
𑜏𑜣 (sī)