Which prefix refers to the number four?

The prefix that refers to the number four is "tetra." This prefix is derived from Greek and is commonly used in various scientific and mathematical contexts. For example, in chemistry, "tetra" is found in the term "tetrachloride," which indicates a compound that contains four chlorine atoms. Similarly, in geometry, a "tetrahedron" is a three-dimensional shape with four triangular faces. This consistent usage across different fields highlights the significance of "tetra" in conveying the concept of four.

The other prefixes have distinct meanings: "poly" refers to many or multiple, "supra" means above or beyond, and "pseudo" indicates false or deceptive. Thus, while they may appear in various contexts, they do not relate to the number four.