Trigonate: three-cornered; approximately triangular.
Trigoneutism: where three broods occur in one season.
Trigonulum: in Odonata, = triangle.
Trimera: that series of Coleoptera, in which there are only three tarsal joints present.
Trimerous: species which have the tarsi three-jointed.
Trinomial: that method of nomenclature in which a varietal or subspecific name follows the specific term without an intervening mark or indications of its rank.
Tripectinate: when an antenna has three branches or processes to each joint.
Triquetral: = triquetrous.
Triquetrous: with three flat sides.
Tri-regional: divided into three distinct parts or regions.