The term "trigonal" refers to a geometric shape or arrangement that has three angles or three sides. In chemistry, it often describes molecular geometry where a central atom is bonded to three other atoms, forming a triangular shape. This arrangement is commonly seen in molecules like boron trifluoride. In addition to chemistry, "trigonal" can also relate to crystals and minerals, where the crystal system is characterized by three equal axes that intersect at 120-degree angles. This symmetry is found in various minerals, such as quartz and calcite, contributing to their unique physical properties.