Consider the introduction to the topic of Calculus as another--truncated--example:
Calculus ... is a branch of mathematics that includes the study of limits, derivatives, integrals, and infinite series.... Historically, it has been referred to as "the calculus of infinitesimals", or "infinitesimal calculus". Most basically, calculus is the study of change, in the same way that geometry is the study of space. ... Calculus builds on algebra, trigonometry, and analytic geometry and includes two major branches, differential calculus and integral calculus, that are related by the fundamental theorem of calculus. In more advanced mathematics, calculus is usually called analysis and is defined as the study of functions.
Calculus is the part of mathematics which looks at things that change over time. It tries to say what type of change it is and how big it is using functions at the exact moment at which the change is taking place. There are two different types of calculus. Differential calculus divides things into small pieces and tells us how they change from one moment to the next, while integral calculus joins the small pieces together and tells us how much of something is made by a change.