What is a model?

Abstract

What do I mean by the word ‘model’, as it is used in this book? We all know what a model is in everyday language, although there may sometimes be some confusion between small three-dimensional representations of railways, roads, cities, vehicles, armies, etc., and those glamorous (and often partly undressed) ladies used in advertisements for clothes and other articles. Needless to say, I am not using the word in either of these two senses. Instead, I will use a somewhat extended interpretation which has been given to the word by scientists, as the representation of relationships between some formally defined quantities or qualities.