tri-
/traɪ/combining form
1- three; having three表示“三”; “三重”：
triathlon.
1.1
- Chemistry (in names of compounds) containing three atoms or groups of a specified kind【化】表示“（化合物名称）三原子的”; “三基的”：
trichloroethane.
词源
from Latin and Greek, from Latin tres, Greek treis 'three'.