Basic Concepts & Definitions
There are concepts, called fundamentals, that form the base of all of physics. Anything that physics describes can be expressed in terms made up only of fundamentals. The fundamentals are not reducible to anything more basic, and are undefinable by definition. The fundamentals therefore are the starting point for our development of a mathematics of motion.
There is a certain element of arbitrary choice in picking what to use for fundamentals. Science seeks simplicity where possible, and fundamentals should be concepts commonly understood as obvious. Also the fundamentals should be as few in number as possible, while still as a group remaining a complete base for the physics built upon them. The fundamentals ...