According to Smith (1988), author of a specialized dictionary on tourism, the word "tourist" was introduced in 1800 and the word "tourism" in 1811. However, what exactly is tourism? Who are the tourists? Although both terms have been part of the English language for over two centuries, there is still no universally recognized effective definition for either of them. For many decades, researchers and practitioners have produced many precise definitions for both “tourist” and “tourism,” but no definition of either term has been widely recognized. According to Smith (1988), he suggests that “there will probably never be a single definition of tourism” as economists, psychologists and geographers perceive certain aspects of tourism in their field (Smith 1988 cited in Leiper 1995:3). However, any approach to defining tourism can be useful for the people who propose it and for those who perceive the world subjectively. In this essay, academic authors such as Krapf and Hunziker (1942), Stear (2005), and McIntosh and Goeldner (1977) each define “tourism” with different methodical approaches. After discussing "tourism", the focus then shifts to "tourists" where again Stear (2005), Leiper (1979) and Weaver and Lawton (2006), define "tourists" and its heuristic concepts. One of the first attempts to define tourism was that of two Swiss academics, professors Hunziker and Krapf of the University of Bern. They defined tourism in a 1942 study as a complex of environmental impacts: "the set of phenomena and relationships deriving from the travel and stay of non-residents, since they do not lead to permanent residence and are not connected to any activity of I earn". This definition has been recognized by many international associations including the International Association of Scientific Experts on Tourism (AIEST). The advantages of this definition are the recognition of wide-ranging impacts; a large number of issues that are studied under the name of "tourism" are based on it. Furthermore, Krapf and Hunziker's definition is highly intellectual as they still manage to distinguish tourism from migration; his theory is based on “travel and stay” on the assumption that this is necessary for tourism, thus preventing day trips. While the definition's approach is reasonable, the definition is considerably “too vague” (Leiper, 1995: 17) as it includes a huge amount of human activity that few thoughtful individuals would consider to fall within the scope of tourism. Because of their broad definition of tourism, prisoners, hospital patients, boarding school students, and soldiers at war can easily fall under the definition, thus highlighting a serious flaw.