The chain rule is a formula for computing the derivative of the composition of two or more functions. It states that if $y = f(g(x))$, then the derivative $dy/dx = f'(g(x)) * g'(x)$.
Derivative: A measure of how a function changes as its input changes; it represents an instantaneous rate of change.
Composite Function: A function formed when one function is substituted into another, such as $f(g(x))$.
Implicit Differentiation: A method used to find derivatives when a function is not given in explicit form, often involving the use of the chain rule.