Our concern in this section is to arrive at a workable definition of ESP. But rather than give a straight answer now to the question ‘What is ESP?’, we would prefer to let it gradually emerge as we work through the section. Let us begin instead with a simpler question: ‘Why ESP?’ After all, the English Language world got along well enough without it for many years, so why has ESP become such an important (some might say the most important) part of English language teaching? In the following three chapters we shall briefly survey the factors which led to the emergence of ESP in the late 1960s and the forces, both theoretical and practical, which have shaped its subsequent development. In Section 2 we shall look in greater detail at the elements we outline in this section.