The airy wave theory is a well-known concept in fluid dynamics that describes the behavior of waves on the surface of a fluid. There are several synonyms for the term "airy wave theory," such as linear wave theory, small-amplitude wave theory, and surface gravity wave theory. Each of these terms refers to the same concept, which is the mathematical description of the motion of the fluid surface under the influence of gravitational forces. While different terms may be used to describe the same phenomenon, they all share the same fundamental principles, and are essential tools in understanding wave behavior and its impact on various engineering applications, such as offshore structures, shipping, and coastal protection.