This book, like the others in the Series, is written in simple English – the language most widely used in science and technology. It builds on the foundations laid in Book 1 (Number and symbols) and in Book 2 (Space) and deals with the mathematics we need in describing the relationships among the quantities we measure in Physics and the Physical Sciences in general. This leads us into the study of relationships and change, the starting point for Mathematical Analysis and the Calculus – which are needed in all branches of Science.