Calculus of Variations: A branch of mathematics that deals with finding the functions that optimize a given functional, such as minimizing the time taken for an object to slide down a curve.
Cycloid:The curve generated by a point on the circumference of a circle as the circle rolls along a straight line. The brachistochrone curve is a special type of cycloid.
Variational Principle: The principle that physical systems tend to evolve in a way that minimizes or maximizes a certain quantity, such as the time taken for an object to slide down a curve.