# Celsius

Celsius is a measurement of temperature. It is also called the Centigrade scale. It was originally defined to be where $0^{\circ}$ Celsius is where water freezes at 1 atm and $100^{\circ}$ Celsius is where water boils at 1 atm.

However different thermometers register slightly different temperatures at these points, so now, two points: the absolute zero and the triple point of water are used to fix the Celsius scale. To avoid incompatibility, absolute zero is defined to be $-273.15^{\circ}$ and the triple point is $0.01^{\circ}$.