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(va-nil′ĭn) [vanilla + -in] A crystalline compound found in vanilla pods or produced synthetically; used for flavoring foods and in pharmaceuticals.

vanishing lung syndrome

Massive, giant bullous emphysema of the lungs.

van’t Hoff, Jacobus Henricus

(vant-hof′) Dutch physical chemist, 1852–1911.

van’t Hoff law The osmotic pressure of a solution is equal to the product of its temperature, the ideal gas constant, and its solute concentration.

van’t Hoff rule 1. The rule that the speed of chemical reactions is doubled, at least, for each 10°C rise in temperature. The rule is an approximation that works best when temperatures approximate those under which the reaction normally occurs. 2. Any substance in a dilute solution exerts an osmotic pressure that is equivalent to the pressure of an equal volume of gas in solution. 3. A technique used to predict the greatest number of mirror-image versions of a molecule that can rotate plane polarized light.


(vāp) [Gr. Vaping. Shortening of vapor, vaporize] To inhale flavored, heated nicotine or other substances (typically in a solvent) via an electronic cigarette.


(vā′pŏr) [L. vapor, steam] 1. The gaseous state of any substance. 2. A medicinal substance for administration by inhalation.


(vā″pŏ-rĭ-zā′shŏn) 1. The conversion of a liquid or solid into vapor. 2. The therapeutic use of a vapor.

laser v. The resection of tissue by converting it to gas with laser energy.

photoselective v. of the prostate A treatment for prostatic hyperplasia in which the prostate gland is vaporized by a laser inserted into the penis via a cystoscope.

transurethral v. of the prostate ABBR: TUVP. A treatment for prostatic hyperplasia in which a laser is used to vaporize hypertrophic prostatic tissue.


(vā′pŏ-rīz″) To change a material to a vapor form.


(vā′pŏ-rī″zer) A device for converting liquids into a vapor spray.


(vā′pŏ-rŭs) [vapor] Pert. to, or producing vapors.


Exposed to steam in order to clean, decontaminate, or sterilize. Clotting factors are steam-treated to remove potentially infectious agents such as pathogenic viruses.


(văk′tă) Hepatitis A vaccine, inactivated.

Vaquez disease

(vă-kez′) [Louis Henri Vaquez, Fr. physician, 1860–1936] Polycythemia vera.


(var″ē-ă-bil′ĭt-ē) [variable] The ability or tendency to change.

baseline v. Fluctations in the fetal ...

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