The term "tetra" comes from the Greek word for "four." It is commonly used in various fields, including mathematics, science, and art, to denote a group or structure consisting of four elements. For example, in geometry, a tetrahedron is a three-dimensional shape with four triangular faces, six edges, and four vertices. In biology, "tetra" often refers to a family of small freshwater fish known as tetras, which are popular in aquariums. These fish are typically colorful and social, making them a favorite among fish enthusiasts. The term can also be found in chemistry, where it describes compounds containing four atoms or groups.