Celsius: relating to the temperature scale in which water freezes at 0 degrees Celsius (0 °C) and boils at 100 °C at standard atmospheric pressure (760 mmHg); the temperature on the Celsius scale is the temperature in kelvins minus 273, and a degree Celsius is equal to a kelvin. Named after the Swedish astronomer Anders Celsius

centigrade: the historical name for the Celsius temperature scale. Named from the Latin (centum = 100, gradus = steps)