## 3 The Ambiguity of Virtual Reality Terminology in Healthcare and Beyond
### Modern Definitions and Concepts of Virtual Reality and Related Technologies
In contrast to the approach in healthcare, which often categorizes VR based on the level of immersion, some authors from other fields argue that VR is inherently immersive and involves experiences where the physical environment is at least visually replaced [40]. These definitions exclude activities such as _\"looking at 3D content on a 2D screen and browsing through it with a mouse\"_[40]. Others contend that a fully immersive VR experience, where no real-world stimuli are perceived, does not exist. Such an experience, they argue, would only be possible in a Matrix-like VR scenario, where both interoceptive and exteroceptive senses are entirely stimulated by technology [42]. Furthermore, according to some definitions, non-immersive experiences classified as VR in healthcare might be more appropriately categorized as AR. For example, [PERSON] and [PERSON], (1994) [68] define AR as _\"an environment that is primarily real but includes virtual elements\"_. Definitions which do not describe AR as an environment that overlaps or blends the virtual and real worlds, suggest that AR could also encompass situations where an individual perceives reality (e.g., themselves and the surrounding physical world) while simultaneously viewing a virtual world. This could include scenarios where an individual is positioned in front of a 2D computer screen, observing a virtual environment--commonly referred to as non-immersive environments in healthcare. In summary, the lack of consensus on the definition of VR in the various application areas remains a problem. It can be said that the understanding of VR in the healthcare sector is somewhat different compared to other sectors. Although it appears that most researchers in healthcare categorize VR based on levels of immersion, notable discrepancies remain within the healthcare field itself, particularly regarding whether the observation of and/or interaction with 3D environments displayed on 2D computer screens should be classified as VR. Overall, the inconsistency in VR terminology highlights the need for researchers and practitioners to precisely define the equipment and methods they use [41]. While detailed descriptions of interventions are valuable, the need for such precision can increase the risk of errors--if an intervention is not thoroughly described, reliance may fall solely on (potentially inaccurate) terminology. Different interpretations of the same terms can lead to the inclusion of various types of interventions under a single label. For example, in the case of non-immersive VR, it is currently unclear whether such environments require interaction from the user or not. Uniformity in terminology would facilitate clearer communication within the field by reducing the need for highly detailed descriptions of the technology used and its intended purpose, ensuring a shared understanding of key concepts. Supplementary Table S1 presents the definitions and descriptions of VR provided in studies investigating its application in the context of musculoskeletal conditions.