Mathematics and Physics Glossary

Vacuometer, n. (Phys.) (a) An instrument for the comparison of barometers. (b) An apparatus for the measurement of low pressures.

-- Vacuum, n.; pl. E. Vacuums, L. Vacua. (Phys.) A space entirely devoid of matter (called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means; as, water boils at a reduced temperature in a vacuum.

-- Vacuum tube (Phys.), a glass tube provided with platinum electrodes and exhausted, for the passage of the electrical discharge; a Geissler tube.

-- Torricellian vacuum. See Torricellian vacuum.

Valid, a. (Math.) Premises or reasoning from which the conclusion may correctly inferred or deduced.

-- Valid proof or statement, n. (Math.) one in which all the arguments leading up to it are correct.

Value, n. (Math.) Any particular quantitative determination; as, a function's value for some special value of its argument.