A REVIEW OF DEFINITIONS OF TOURISMThe academic study of tourism is relatively young (Echtner & Jamal, 1997): related terms (such as "tourism" and "tourists") first appeared in the early nineteenth century (Smith, 1988). Tourism research evolved thereafter and now fits into numerous domains (Echtner & Jamal, 1997). The field is inherently multidisciplinary (Tribe, 1997), dating back to its roots primarily in such fields as economics, sociology, anthropology, and others (Kozak & Kozak, 2016). Considering the area's multifaceted nature, tourism scholars began to ask the question "What is tourism?" after identifying it as a globalized phenomenon with evident socioeconomic importance worldwide (Darbellay & Stock, 2012;Smith, 1988).Smith 's (1988) question "What is tourism?" has attracted a spate of answers but remains hotly debated. Definitions of tourism continue to emerge. As a seminal example, Leiper (1979) centered tourism on geography: he defined tourism as "the system involving the discretionary travel and temporary stay of persons away from their usual place of residence for one or more nights, excepting tours made for the primary purpose of earning remuneration from points en route" (pp.403-4). This system is composed of travelers, generating and destination regions, transit routes, and the general tourist industry, all of which feature functional and spatial links. The United Nations World Tourism Organization (UNWTO) (2019) later described tourism as people leaving their everyday environment for no more than a full year. Tourism also reflects travel motivations, which do not always involve pleasure and relaxation (C. Yu, Wen, & Meng, 2020). Other drivers of travel include health (for example, medical tourism), human rights (for example, social tourism), grief (for example, dark tourism), and professional development (for example, business and education) (see for example Connell, 2013;Glover, 2011;McCabe & Diekmann, 2015).Researchers have proposed different tourism-related areas to examine the field more closely (Yuan, Gretzel, & Tseng, 2015). Sample topics include tourism geographies, tourism economics, and physics and tourism. For example, some studies (Cui, Huang, Chen, Zhang, & Li, 2019; Cui, Xin, & Li, 2021) have borrowed the concept of "inertia" from physics: inertia leads an object to maintain its velocity unless influenced by external forces. The concept has been applied in consumer-based studies (as