"Second-order" refers to a concept in various fields, including mathematics, physics, and systems theory. In mathematics, it often describes a type of equation or derivative that involves the second degree, such as a quadratic equation. In systems theory, second-order systems are those that respond to inputs with a specific behavior, often characterized by oscillations or damping. In the context of feedback and control systems, second-order refers to the complexity of the system's response. A second-order system typically has two energy storage elements, which can lead to more intricate dynamics compared to first-order systems. Understanding second-order behavior is crucial in designing stable and efficient systems, such as in engineering and robotics.