calculus

branch of

The Opposite of Infinity - Numberphile (youtube.com) Continuing to talk Infinitesimals, this time with Dr James Grime.

Calculus Made Easy by Silvanus P. Thompson (gutenberg.org)
derivative
In 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became calculus.
The calculus was the first achievement of modern mathematics and it is difficult to overestimate its importance. I think it defines more unequivocally than anything else the inception of modern mathematics, and the system of mathematical analysis, which is its logical development, still constitutes the greatest technical advance in exact thinking. John von Neumann, in James R. Newman The World of Mathematics

Calculus (Wikipedia) Calculus is the mathematical study of continuous change, in the same way that geometry is the study of shape, and algebra is the study of generalizations of arithmetic operations.