The term "trigonal" refers to a geometric shape or arrangement that has three angles or three sides. In chemistry, it often describes the molecular geometry of a molecule where a central atom is bonded to three other atoms, forming a triangular shape. This arrangement can be seen in molecules like boron trifluoride. In addition to chemistry, "trigonal" can also relate to crystals and minerals. For example, the trigonal crystal system is one of the seven crystal systems in crystallography, characterized by three equal axes that intersect at 120-degree angles. This system includes minerals like quartz and calcite.