Who discovered ‘calculus’?

Calculus is a branch of mathematics which studies ‘change’. Accordingly, it deals with limits, derivatives, functions and indefinite series that explain ‘change’. Isaac Newton and Gottfried Wilhelm Leibnitz independently invented calculus. Newton used calculus fundamentally to arrive at the universal law of gravitation, and then to solve the problem of planetary motion, the shape of the surface of a rotating fluid, the oblateness of the earth, the motion of a weight sliding on a cycloid, and also to explain various other interesting phenomena. Leibnitz provided a clear set of rules for manipulating infinitesimal quantities, allowing the computation of second and higher derivatives, and providing the product rule and chain rule, in their differential and integral forms.