The term 'DERIVATIVE' is a mathematical concept that refers to the rate of change of a function with respect to one of its variables. It is used to measure how quickly a function changes as its input changes. Derivatives are also used in calculus to find the maximum or minimum values of a function. In finance, derivatives are used to hedge against risk and to speculate on the future value of an asset. The crossword solution for the term 'DERIVATIVE' is 'ABNORMAL', which is fitting since derivatives are often used to measure the ABNORMAL behavior of a function.