Zē′ro, n.

n. [Fr. zéro, It. & Sp. zero, from Ar. çafrun, çifrun, empty, a cipher, q. v.] Cipher; nothing; naught; the point from which the graduation, as of a thermometer, commences.

Zero, in the thermometers of Celsius and Réaumur, is at the point at which water congeals. The zero of Fahrenheit’s thermometer is fixed at the point at which the mercury stands when immersed in a mixture of snow and common salt. In Wedgwood’s pyrometer, the zero corresponds with 1077° on Fahrenheit’s scale.

Zero-point, the point indicating zero, or the commencement of a scale or reckoning.