According to the Oxford English Dictionary
"virtual" has had numerous meanings, the most relevant for our inquiry are
That [which] is so in essence or effect, although
not formally or actually; admitting of being called by the name so far as
the effect or result is concerned.
Optics. Applied to the apparent focus or image resulting from the
effect of reflection or refraction upon rays of light.
Computers. Not physically existing as such but made by software to
appear to do so from the point of view of the program or the user;
spec. applied to memory that appears to be internal although most of
it is external, transfer between the two being made automatically as
1. a. Possessed of certain
physical virtues or capacities; effective in respect of inherent natural
qualities or powers; capable of exerting influence by means of such
qualities. Now rare.
- 1398 Trevisa
Barth. De P.R. xix. viii. (Bodl. MS.), But vertual li3t
igadered in a litel place or in a pointe is cleped moche li3t.
- 1477 Norton Ord. Alch. v. in Ashm. (1652) 62 But our
chiefe Digesture for our intent, Is virtuall heate of the matter digerent.
- A. 1593 Marlowe Hero & Leander iii. 89 So to
all objects..his senses' flame Flowd from his parts with force so virtuall,
It fir'd with sence things weere insensuall.
- 1626 Bacon
Sylva §326 See if the Virtuall Heat of the Wine, or Strong
Waters will not mature it;
- 1657 R. Ligon Barbadoes (1673)
106 Though the virtual beams of the Sun, give growth and life to all the
Plants and Flowers it shines on.
- 1675 E. Wilson Spadacrene
Dunelmensis Pref., Even ordinary water admits of a virtual mixture at
least, as Experience evidenceth in Chalybeate waters.
Meredith Odes Fr. Hist. 91 It was the foreign France the unruly
feared,..Not virtual France, the France benevolent, The
b. Of herbs: Possessing specific virtues.
- 1660 F. Brooke Le Blanc's
Trav. 364 To Rivers they sacrifice the shels that come from them, to
fountains fruits and vertual herbs.
- 1830 T. Aird Captive of
Fez iii, She knew..every virtual plant, and every sovereign
flower Beneath the moon.
Morally virtuous. Obs.
- C. 1425 Wyntoun
Cron. vii. 1218 His awyn oysse to lif wertual, May mirroure
and ensample be Til alkyn statis.
- C. 1425 Wyntoun Cron.
vii. viii. 2206 Iohun of Salerne, prest cardynale, Commendit a
- 1607 Dekker Wh. of Babylon Wks. 1873 II.
216 You by your heauenly Influence change his vilenes Into a vertuall habit
fit for vse.
3. a. Capable
of producing a certain effect or result; effective, potent, powerful.
- 1432-50 tr. Higden (Rolls)
II. 177 For a man and the worlde be assimilate in iij. thynges, in dimension
diametralle.., in disposicion naturalle, and in operation virtualle.
- 1432-50 tr. Higden 185.
- 1526 Pilgr.
Perf. (Pynson) iii. ix. 47 b, That is called after Saynt Thomas
virtuall attencyon which causeth a person in the begynnyng of his prayer to
haue an actuall consideracion of the prayer or duety that he hath to do.
- 1619 W. Sclater Exp. 1 Thess. (1630) 37 So vertuall was
the speech of Paul a Prisoner, in the heart of his Judge.
Shirley Arcadia iv. iii, I meant it A draught for false
Zelmane, it being virtual To increase affection.
- 1672 Josselyn
New Eng. Rarities 12 The Loone is a Water Fowl, alike in shape to the
Wobble, and as virtual for Aches.
- 1683 Moxon Mech. Exerc.,
Printing i, Dr. Dee..as a vertual Proof of his own Learned Plea, quotes
two Authentique Authors.
b. Mech. (See
- 1815 J. Smith Panorama Sci. &
Art II. 124 Whatever is the real length of the leg b a [of a
siphon], the virtual or acting length when in use, only extends from
b to the surface of the fluid.
- 1825 J. Nicholson Oper.
Mech. 67 The velocity..due to a head of 15 inches; and this we call the
virtual or effective head.
4. a. That is so in essence or effect,
although not formally or actually; admitting of being called by the name so
far as the effect or result is concerned.
- 1654 Jer. Taylor Real Pres. 21 We affirm that
Christ is really taken by faith,..they say he is taken by the mouth, and
that the spiritual and the virtual taking him in virtue or effect is not
sufficient, though done also.
- 1664 Jer. Taylor Dissuas.
Popery ii. §8 But even this attention is not necessary that it
should be actual, but it suffices to be virtual;
- 1697 Burghope
Disc. Relig. Assemb. 166 We shall find it to amount to no less than a
vertual renunciation of our baptism.
- 1734 Waterland Diss.
Exist. First Cause 30 Every Proof a priori proceeds by Causes
either real or virtual.
- 1769 Burke Obs. Pres. St. Nat.
Wks. 1842 I. 112 One part of it could not be yielded..without a virtual
surrender of all the rest.
- 1787 Bentham Def. Usury viii.
73 Heading, Virtual Usury allowed.
- 1820 Milner Suppl.
Mem. Eng. Cath. 132 To prevent the virtual choice of a Catholic Bishop
by an A-Catholic Ministry.
- 1844 H. H. Wilson Brit. India
III. 211 He had reigned thirty-three years, during the first ten of which he
was virtual sovereign of the greater part of Hindustan.
- 1883 A.
Barratt Phys. Metempiric 157 The simplest conscious action involves
actual or virtual thought.
b. Virtual Church, a
council or similar body acting in the name of the whole church. Also
ellipt. as sb.
- 1646 J. Maxwell
Burden of Issachar 20 Whatsoever power..the Catholike Church, or her
virtuall and Representative, an oecumenical Councel, justly challengeth,
this general Assembly vindicateth to it selfe.
- 1646 J. Maxwell
Burden of Issachar 45 It was not consented to by the Church: that is,
the Virtuall Church, the Generall Assemblie.
- 1654 Bramhall
Just Vind. viii. (1661) 230 In all which..they understand..the
virtual Church which is inuested with Ecclesiastical power, that is, the
Pope with his Cardinals and Ministers.
c. Optics. Applied to the apparent focus or image
resulting from the effect of reflection or refraction upon rays of
- 1704 J.
Harris Lex. Techn. I, Virtual Focus, or Point of
Divergence in a Concave Glass.
- 1728 Chambers Cycl.,
Point of Dispersion, is that wherein the Rays begin to diverge;
usually call'd the Virtual Focus.
- 1808 J. Webster Nat.
Philos. 185 They issued from the virtual focus in the axis of the lens.
- 1831 Brewster Optics i. 11 The point A', behind the
mirror..is called their virtual focus, because they only tend to meet
in that focus.
- 1874 Lommel's Light 90 The lenses of the
second group have virtual foci.
- 1831 Brewster Optics ii. 18 In convex mirrors the image is
always a virtual one formed behind the mirror.
- 1859 Parkinson
Optics (1866) 130 A familiar instance of a virtual image is
that formed by a common looking-glass of an object in front of it:-the image
of an object under water is virtual.
- 1885 Buck's
Handbk. Med. Sci. I. 39/1 If their direction, after the refraction, be
prolonged backward, their prolongations meet to form a virtual
d. Dynamics. Of velocity or moment (see quot.
1867). virtual displacement, any notional, infinitesimal
displacement in a mechanical system that is consistent with the constraints
of the system; virtual work, the work done by a force making a
- 1818 Barlow in
Encycl. Metrop. (1845) III. 41/1 [The] principle..of virtual
velocities..is now, by most foreign writers, made the foundation of the
whole theory of statics.
- 1843 Penny Cycl. XXVI. 373/2 The
name of the principle of virtual velocities..is very ill fitted to express
the idea which is to be conveyed. [Full account follows.]
Thomson & Tait Nat. Phil. I. i. §237 If the point
of application of a force be displaced through a small space, the resolved
part of the displacement in the direction of the force has been called its
- 1867 Thomson & Tait Nat. Phil., I.
i. §237 The product of the force, into the virtual velocity of
its point of application, has been called the Virtual Moment of the
- 1877 G. M. Minchin Treat. Statics iv. 61 The virtual
work of a force is the product of the force and the projection along its
direction of the virtual displacement of its point of application.
- 1897 A. E. H. Love Theoret. Mech. viii. 139 Principle of
Virtual Work. The sum of the virtual works of all the forces on a system in
equilibrium vanishes in every infinitesimal displacement.
Synge & Griffiths Princ. Mech. ii. 60 Although the chief merit of
the principle of virtual work lies in the fact that it does not involve the
reactions of constraints, nevertheless it can be used to find these
reactions should they be required.
- 1981 R. R. Craig Structural
Dynamics ii. 28 Use the principle of virtual displacements to derive the
equation of motion of the idealized system shown below.
Nucl. Physics. Applied to an excited state of an atomic nucleus
which has energy in excess of that needed for the emission of a particle but
a lifetime sufficiently long for it to be regarded as a quasi-stationary
- 1931 Proc. R. Soc. A. CXXXIII.
228 According to the theory..the emission of <alpha>- particles by
radio active nuclei is to be explained by the assumption that there exists
in the nucleus a `virtual' level of positive energy, which is occupied by an
- 1955 I. Kaplan Nucl. Physics xvi.
368 Each excited state of the compound nucleus, whether bound or virtual,
has a certain mean lifetime.
- 1963 W. E. Burcham Nucl.
Physics ix. 372 All nuclear levels, except the ground state, can in
principle emit radiation, leaving the nucleus in a less highly excited
state, and virtual levels can in addition emit particles.
Particle Physics. Applied to particles and processes that cannot be
directly detected and occur over very short intervals of time and space with
correspondingly indefinite energy and momenta, which are not necessarily
conserved within the time involved.
Physical Rev. LXXV. 1305/2 These divergent terms must now be
interpreted as renormalization or modification of the electric charge of the
proton due to virtual mesons.
- 1961 W. S. C. Williams Introd.
Elementary Particles xiii. 341 If the incident photon is 140 Mev and the
positron is emitted at 90° with an energy of 100 Mev, then the
four-momentum of this virtual electron is about 140 Mev/c;
Sci. Amer. June 71/3 Although it may seem that virtual particles
violate fundamental conservation laws, the violation is closely delimited to
those areas where the uncertainty principle applies.
- 1973 L. J.
Tassie Physics Elementary Particles viii. 15 The electron now
consists of its `bare' self together with all its virtual interactions with
the electromagnetic field, corresponding to the electron emitting and
re-absorbing virtual photons.
- 1973 Sci. Amer. Oct. 110/1
The scattering of the two electrons is described by saying that these
particles exchange a virtual photon that transfers momentum from one
particle to the other.
- 1979 D. R. Hofstadter Gödel,
Escher, Bach (1980) v. 146 To understand how a real, physical electron
propagates..the physicist has to be able to take a sort of average of all
the infinitely many different possible drawings which involve virtual
g. Computers. Not physically existing as such but
made by software to appear to do so from the point of view of the program or
the user; spec. applied to memory that appears to be internal
although most of it is external, transfer between the two being made
automatically as required.
Proc. Eastern Joint Computer Conf. xvi. 82/2 The sole function of the
virtual memory is to increase machine speed.
- 1966 R. Adair et al.
IBM Cambridge Scientific Center Rep. No. G320-2007 (title) A
virtual machine system for the 360/40.
- 1966 IBM Systems
Jrnl. V. 79 A virtual-storage computer (vsc) can decode addresses that
are longer than those of its memory. The longer address is treated..as a
virtual address that must be transformed to the actual, shorter memory
address... The virtual addressing of the word in external storage triggers a
procedure that automatically brings the addressed word into memory.
- 1972 Computer Jrnl. XV. 199/2 Our system runs in a virtual
machine, which is implemented by an interpreter. We can therefore easily
add new instructions to our virtual hardware, merely by extending the
- 1973 P. B. Hansen Operating System Princ. i.
3 An operating system makes a virtual machine available to each user... The
simultaneous presence of several users makes the virtual machines much
slower than the physical machine.
- 1981 Pohl & Shaw Nature
of Computation vi. 198 The Algolic language defines an Algolic virtual
machine that may be implemented on a variety of computers. The Algolic
machine could be constructed with the following software on a particular
- 1982 G. Lee From Hardware to Software xxvi. 444
In a multi-programming system, several programs are being executed `at
once'... Thus the operating system has to make available to each user a
virtual store, of which he appears to be the sole user.
80 Microcomputing Feb. 232/2 Virtual-memory systems have been
prevalent in main-frames and large minicomputers for at least a decade.
- 1985 Which Computer? Apr. 54/1 No doubt this is a side
effect of using the disc as a virtual memory.
collocations: virtual cathode (Electronics), a part of a space charge
or electron beam where the potential is a minimum, so that electrons are
repelled and positive ions attracted; virtual height, the height of
an imaginary reflecting plane surface which in free space would give rise to
the same travel time for reflected radio waves as an actual ionospheric
layer; virtual temperature (Meteorol.) [tr. F. température
virtuelle (Guldberg & Mohn Études sur les Mouvements de l'
Atmosphère (1876) i. i. 6)] , the temperature that dry
air would have to have in order to have the same density as a given body of
moist air when at the same pressure.
*Virtual cathode [see suppressor
- 1964 New Scientist 1 Oct. 29/1 It was found that a
virtual cathode could be obtained with a beam current of 3.5 milliamperes or
more, and that its relaxation time was in fact inversely proportional to
- 1928 Proc. IRE XVI. 85 The heights as given
in this paper are *virtual heights. They are calculated on the assumption
that ordinary reflection takes place and that the layer is parallel to the
- 1967 [see ionogram
- 1975 D. G. Fink Electronics Engineers' Handbk.
xviii. 107 The reflection process for plane ionosphere is
equivalent to mirror-type reflection at a height equal to the virtual height
h' of reflection of the equivalent vertical frequency.
- 1910 C. Abbe tr. Guldberg & Mohn in Smithsonian Misc.
Collections LI. No. 4. 124 We call the quantity T the *virtual
temperature; for dry air the virtual temperature is the same as the absolute
- 1957 G. E. Hutchinson Treat. Limnol. I. vii.
468 C represents the virtual temperature of isothermal circulation
prior to the development of stratification in the early summer.
- 1979 L. J. Battan Fund. Meteorol. v. 83 The effects of
humidity can be taken into account by employing a quantity called the