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In calculus (a branch of mathematics), a differentiable function of one real variable is a function whose derivative exists at each point in its domain.
Calculus has widespread uses in science, economics, and engineering and can solve many problems that algebra alone cannot. Calculus is a major part of modern mathematics education. A course in calculus is a gateway to other, more advanced courses in mathematics devoted to the study of functions and limits, broadly called mathematical analysis. Calculus has historically been called the calculus of infinitesimals, or infinitesimal calculus. The word calculus comes from Latin and means a small stone used for counting. More generally, calculus refers to any method or system of calculation guided by the symbolic manipulation of expressions.