The Celsius scale initially defined as the freezing point of water and as the melting point of ice, is now officially a derived scale, defined in relation to the Kelvin temperature scale. This is the scale used in most countries in the world. This scale was proposed by Anders Celsius to the Royal Swedish Academy of Sciences in 1742. In this document it was stipulated that 0°C would correspond to the boiling temperature of the water and 100°C to the melting temperature of the ice. It was not until later that these values were reversed. Initially, the degrees of the Celsius scale were denominated degrees centigrade, only in 1948 and that they happened to have the official designation of degrees Celsius.
The Kelvin scale was proposed in 1848 by Lord Kelvin, who wrote an article on the need for a scale where the "infinite cold" (known as absolute zero) was the zero point of the scale. This point was set to -273.15°C. With this, the Kelvin temperature scale became the only one where there were no negative values. Unlike the Celsius and Fahrenheit scale, the temperatures described in Kelvin are not accompanied by the word "degrees". Therefore, one should not say 250 degrees Kelvin, but one should mention only 250 Kelvin or 250 K.