Partial derivatives are a fundamental concept in calculus, particularly in the study of functions of multiple variables. They measure how a function changes as one of its variables is varied while keeping the other variables constant. This is crucial in fields like physics and engineering, where systems often depend on several factors. For example, in a function f(x, y), the partial derivative with respect to x is denoted as ∂f/∂x. This notation indicates the rate of change of f as x changes, while y remains fixed. Understanding partial derivatives allows for better analysis of complex systems and optimization problems.