The notation "dy/dx" represents the derivative of a function, indicating how the value of one variable, y, changes in relation to another variable, x. It is a fundamental concept in calculus, used to analyze the rate of change and the slope of curves. Essentially, it measures how steep a function is at any given point. In practical terms, "dy/dx" helps in understanding various phenomena, such as velocity in physics or growth rates in biology. By calculating this derivative, one can predict future behavior of systems and optimize processes in fields like engineering and economics.