Mathematics is the science of numbers, it involves such areas as counting quantity, studying relationships between numbers and relationships in space, and study of structure, rates of change, and time. It includes the fields of Algebra (relationships between numbers), Geometry (relationships in space), Trigonometry (the study of triangles), and Calculus (rates of change). Most mathematical concepts are designed for practical applications such as financial accounting, geometric construction of building, astronomical calculations, calendar dating, telling time, engineering, physics, chemistry, etc. But some mathematicians have developed mathematical concepts without practical applications in mind. The former is called applied mathematics, the latter is called pure mathematics.