ABSTRACT
Historically, the concept of a function evolved over time. The word “function” (or more precisely, its Latin equivalent) was used in mathematics for the first time in 1694 by Gottfried Leibniz. Initially, a function denoted any quantity associated with a curve such as the coordinates of a point on the curve, the slope of the curve, etc. By 1718 at the latest, Johann Bernoulli (1667-1748) viewed a function as an expression which involves a variable and some constants. Later, Euler thought of a function as an equation or formula consisting of variables and constants. In 1734, Euler introduced the now familiar notation f(x) to denote a function in one variable. The present set theoretic definition of a function is due mainly to Gustav Peter Lejeune Dirichlet (1805-1859).
