In mathematics, particularly in calculus, 'Partial' refers to partial derivatives, which are used to analyze functions of multiple variables. A partial derivative measures how a function changes as one of its variables changes while keeping the other variables constant. This concept is essential in fields such as physics and engineering, where systems often depend on several factors. Partial derivatives are denoted by the symbol ∂ and are fundamental in optimization problems and in the study of multivariable functions. They help in understanding the behavior of complex systems and are crucial for developing models in various scientific disciplines.