This is an excerpt from my 2018 book chapter: https://www.academia.edu/41628237/Chapter_12_VR_AR_and_Video_360_A_Case_Study_Towards_New_Realities_in_Education_by_Plamen_Miltenoff 

Among a myriad of other definitions, Noor (2016) describes Virtual Reality (VR) as “a computer generated environment that can simulate physical presence in places in the real world or imagined worlds. The user wears a headset and through specialized software and sensors is immersed in 360-degree views of simulated worlds” (p. 34).   

Noor, Ahmed. 2016. “The Hololens Revolution.” Mechanical Engineering 138(10):30-35. 

Weiss and colleagues wrote that “Virtual reality typically refers to the use of interactive simulations created with computer hardware and software to present users with opportunities to engage in environments that appear to be and feel similar to real-world objects and events” 

Weiss, P. L., Rand, D., Katz, N., & Kizony, R. (2004). Video capture virtual reality as a flexible and effective rehabilitation tool. Journal of NeuroEngineering and Rehabilitation, 1(1), 12. https://doi.org/10.1186/1743-0003-1-12 

Henderson defined virtual reality as a “computer based, interactive, multisensory environment that occurs in real time”  

Rubin, 2018, p. 28. Virtual reality is an 1. artificial environment that’s 2. immersive enough to convince you that you are 3. actually inside it.
”artificialenvironment ” could mean just about anything. The photograph is an artificial environment of video game is an artificial environment a Pixar movie is an artificial environment the only thing that matters is that it’s not where are you physically are.  p. 46 “VR is potentially going to become a direct interface to the subconscious”

1. p. 225 Virtual reality: the illusion of an all-enveloping artificial world, created by wearing an opaque display in front of your eyes.  

From: https://blog.stcloudstate.edu/ims/2018/11/07/can-xr-help-students-learn/ : 
p. 10 “there is not universal agreement on the definitions of these terms or on the scope of these technologies. Also, all of these technologies currently exist in an active marketplace and, as in many rapidly changing markets, there is a tendency for companies to invent neologisms around 3D technology.” p. 11 Virtual reality means that the wearer is completely immersed in a computer simulation.

from: https://blog.stcloudstate.edu/ims/2018/11/07/can-xr-help-students-learn/ 

There is no necessary distinction between AR and VR; indeed, much research
on the subject is based on a conception of a “virtuality continuum” from entirely
real to entirely virtual, where AR lies somewhere between those ends of the
spectrum.  Paul Milgram and Fumio Kishino, “A Taxonomy of Mixed Reality Visual Displays,” IEICE Transactions on Information Systems, vol. E77-D, no. 12 (1994); Steve Mann, “Through the Glass, Lightly,” IEEE Technology and Society Magazine 31, no. 3 (2012): 10–14.

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Among a myriad of other definitions, Noor (2016) describes Virtual Reality (VR) as “a computer generated environment that can simulate physical presence in places in the real world or imagined worlds. The user wears a headset and through specialized software and sensors is immersed in 360-degree views of simulated worlds” (p. 34).   Weiss and colleagues wrote that “Virtual reality typically refers to the use of interactive simulations created with computer hardware and software to present users with opportunities to engage in environments that appear to be and feel similar to real-world objects and events.”
Rubin takes a rather broad approach ascribing to VR: 1. artificial environment that’s 2. immersive enough to convince you that you are 3. actually inside it. (p. 28) and further asserts “VR is potentially going to become a direct interface to the subconscious” (p. 46). 
Most importantly, as Pomeranz (2018) asserts, “there is not universal agreement on the definitions of these terms or on the scope of these technologies. Also, all of these technologies currently exist in an active marketplace and, as in many rapidly changing markets, there is a tendency for companies to invent neologisms.” (p. 10) 

Noor, Ahmed. 2016. “The Hololens Revolution.” Mechanical Engineering 138(10):30-35. 

Pomerantz, J. (2018). Learning in Three Dimensions: Report on the EDUCAUSE/HP Campus of the Future Project (Louisville, CO; ECAR Research Report, p. 57). https://library.educause.edu/~/media/files/library/2018/8/ers1805.pdf 

Rubin, P. (2018). Future Presence: How Virtual Reality Is Changing Human Connection, Intimacy, and the Limits of Ordinary Life (Illustrated edition). HarperOne. 

Weiss, P. L., Rand, D., Katz, N., & Kizony, R. (2004). Video capture virtual reality as a flexible and effective rehabilitation tool. Journal of NeuroEngineering and Rehabilitation, 1(1), 12. https://doi.org/10.1186/1743-0003-1-12