## 3 The Ambiguity of Virtual Reality Terminology in Healthcare and Beyond
### Modern Definitions and Concepts of Virtual Reality and Related Technologies
Based on the up-to-date definition by [PERSON] et al., (2023) [43], any interaction with a 3D environment appears to qualify as VR, regardless of whether it is displayed on a 2D computer screen or through HMD. In contrast, modern definitions developed outside of healthcare, such as the one proposed by [PERSON] et al., (2022) [40], limit VR to experiences where the user _\"does not see the physical environment and is, at least visually, sealed off from the physical environment\"_. This suggests that the understanding of VR in healthcare somewhat diverges from how VR is interpreted in other fields. One possible explanation for this discrepancy is the frequent use of various types of XR technologies in industry, particularly for training, simulations, and entertainment, where more immersive technologies often take center stage. In contrast, applications in healthcare tend to rely more on non-immersive approaches, such as _Nintendo Wii_ games, a technology whose production in the industry ended in 2013. When it comes to immersive experiences, healthcare primarily utilizes immersive VR, while the use of MR and AR currently lags behind. This is likely due to the increasing accessibility of immersive VR, whereas MR and AR remain relatively recent developments. Figure 2: The current state of umbrella terms with the most common understanding and contemporary proposals for the meaning of VR and related technologies. VR and related technologies, such as augmented reality (AR) and mixed reality (MR), are commonly grouped under the umbrella term XR. This abbreviation refers to “extended reality”, “cross reality”, or “X-reality”, with no significant difference in meaning between these terms. Under the umbrella of XR, VR and AR are the most frequently included components, with their combination forming MR (as shown in point 1 in Figure 2). In healthcare, this understanding of the relationships between VR, AR, and MR is the most widely accepted, where VR is further categorized based on the level of immersion, ranging from non-immersive to immersive VR. Recently, [PERSON] et al., (2022) [40] distinguished VR and AR across two separate continua (see point 2 in Figure 2). According to their framework, VR spans from atomistic VR, which prioritizes specific goals over user experience, to holistic VR, characterized by immersive experiences that are indistinguishable from real-world interactions. In contrast, AR is described as ranging from assisted AR, where virtual objects are clearly artificial overlays on real-world objects, to MR, where the integration of virtual and real objects becomes indistinguishable. In contrast, [PERSON] et al., (2021) [42] proposed “mixed reality” as the umbrella term, building upon and updating the framework introduced by [PERSON] and [PERSON] in 1994 [68]. According to their understanding, MR encompasses environments where real-world and virtual objects and stimuli are presented together within a single percept. MR environments where the real world is augmented with virtual content are referred to as AR, while environments where most content is virtual but there is some inclusion of real-world elements are termed augmented virtuality (AV). Under this interpretation, MR also encompasses VR, which they term an “external virtual environment (VE)” that includes only the stimulation of exteroceptive senses. At the far-right end of the continuum lies “Matrix-like VE”, which is excluded from MR (along with the purely real environment on the left end) and represents a simulation of both exteroceptive and interoceptive senses, a level of immersion that cannot be achieved in the real world. Although studies uniformly describe the categorization of VR based on levels of immersion, there is inconsistency in how these terms are defined. For instance, non-immersive VR is commonly described as a virtual environment projected onto a 2D display screen [4; 36; 65; 70; 71].