"Bilateral" refers to something that involves two sides or parties. In various contexts, it can describe agreements, relationships, or actions that require cooperation between two entities. For example, a bilateral trade agreement is a deal between two countries to exchange goods and services under mutually agreed terms. In biology, "bilateral" often describes organisms with symmetrical body structures, such as humans and many animals. These organisms have a left and right side that mirror each other, which is important for their movement and function. This symmetry can be contrasted with radial symmetry, where body parts are arranged around a central axis.