- A prefix meaning three, thrice, threefold; as in tricolored,
tridentate. - 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.
- A prefix (also used adjectively) denoting the combination
of constituents (especially electro-negative and electro-positive
bodies) in the proportion of two to three; as, a subsesqui acetate, i.
e., a salt having two equivalents of acetic acid to three of the base.