Zero

(ze'ro.) (It.] The point of a thermometer from which it is graduated. The Z. of Fahrenheit's thermometer is fixed at the point at which the mercury stands when immersed in a mixture of snow and common salt, 32° below the freezing-point. In Wedgwood's pyrometer, the Z. corresponds with 1077.5° on Fahrenheit's scale. The Z. of Reaumur's and of the Centigrade thermometers is the point at which water congeals. [s. 977]