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The term virtual is a concept applied in many fields with somewhat differing connotations, and also, differing denotations.
Colloquially, virtual is used to mean almost, particularly when used in the adverbial form e.g. "That's virtually [almost] impossible".
By extension to the original philosophical definition, the term virtual has also come to mean "modeling through the use of a computer", where the computer models a physical equivalent. Thus, a virtual world models the real world with 3D structures and virtual reality seeks to model reality, enhancing a virtual world with mechanisms for eye and hand movements. The word 'virtual' now modifies numerous nouns for real world concepts: virtual appliance, virtual museum, virtual learning environment (VLE), virtual studio, and so on.
All virtual creations presuppose a basic imitation of reality. Virtual worlds are considered not to be “real” in the concrete sense. A virtual world, for example, does concretely exist as a series of electronic impulses on at least one piece of hardware. So when we refer to something as “virtual”, it may be more helpful to think of the idea in terms of tangibility: we conceptualize that which we cannot physically alter or experience (without, in this case, electronic mediation) as “virtual”. A virtuality, then, can be conceptualized alternatively as “a physical equivalent or model which resists tangibility"—in other words, [a physical equivalent or model] which resists touch.
Virtuality can also be thought of in psychosomatic terms: where the subjective imaginary begins to directly affect the body. Psychosomatic virtuality, in cases such as the placebo effect, challenges the notion of mind/body dualism.
The use of the word virtual for computer simulation of reality is not merely recent. The Online Etymology Dictionary reports that the sense of "not physically existing but made to appear by software" appears as early as 1959.