Tri– (?). [Gr. τρι- or L. tri-, sometimes through French; akin to L. tres three, and E. three. See Three.]
1. A prefix meaning three, thrice, threefold; as in tricolored, tridentate.
2. (Chem.) A prefix (also used adjectively) denoting three proportional or combining part, or the third degree of that to the name of which it is prefixed; as in trisulphide, trioxide, trichloride.