Virtual image. (Optics) See under Image.Virtual moment(of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; — sometimes called virtual work.Virtual velocity (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length.Virtual work. (Mech.) See Virtual moment, above.

(Vir`tu*al"i*ty) n. [Cf. F. virtualité.]

1. The quality or state of being virtual.

2. Potentiality; efficacy; potential existence. [Obs.]

In one grain of corn, there lieth dormant a virtuality of many other.
Sir T. Browne.

(Vir"tu*al*ly) adv. In a virtual manner; in efficacy or effect only, and not actually; to all intents and purposes; practically.

(Vir"tu*ate) v. t. To make efficacious; to give virtue of efficacy. [Obs.] Harvey.

(Vir"tue) n. [OE. vertu, F. vertu, L. virtus strength, courage, excellence, virtue, fr. vir a man. See Virile, and cf. Virtu.]

1. Manly strength or courage; bravery; daring; spirit; valor. [Obs.] Shak.

Built too strong
For force or virtue ever to expugn.

2. Active quality or power; capacity or power adequate to the production of a given effect; energy; strength; potency; efficacy; as, the virtue of a medicine.

Jesus, immediately knowing in himself that virtue had gone out of him, turned him about.
Mark v. 30.

A man was driven to depend for his security against misunderstanding, upon the pure virtue of his syntax.
De Quincey.

The virtue of his midnight agony.

3. Energy or influence operating without contact of the material or sensible substance.

She moves the body which she doth possess,
Yet no part toucheth, but by virtue's touch.
Sir. J. Davies.

4. Excellence; value; merit; meritoriousness; worth.

I made virtue of necessity.

In the Greek poets, . . . the economy of poems is better observed than in Terence, who thought the sole grace and virtue of their fable the sticking in of sentences.
B. Jonson.

been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it.

  By PanEris using Melati.

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