A spring constant, denoted as k, is a measure of a spring's stiffness. It quantifies how much force is needed to stretch or compress the spring by a certain distance. The higher the spring constant, the stiffer the spring, meaning it requires more force to change its shape. The relationship between force and displacement in springs is described by Hooke's Law, which states that the force exerted by a spring is directly proportional to the distance it is stretched or compressed. In mathematical terms, Hooke's Law can be expressed as F = kx, where F is the force applied, k is the spring constant, and x is the displacement from the spring's equilibrium position. This principle is fundamental in various applications, including mechanical systems, automotive suspensions, and even in everyday items like pens and toys. Understanding spring constants helps in designing systems that require specific force and displacement characteristics.