Key Difference: Celsius and centigrade are different terms referring to the same temperature scale. Centigrade has be phased out and replaced to Celsius by the CGPM (Conference General des Poids et Measures) in 1948.

Have you noticed that some people read 35°C as 35 degree Celsius, while other people might read the same exact measurement as 35 degree centigrade? Well, Celsius and centigrade can be a tricky thing to understand, but the important point is that both terms mean the same thing.

The Celsius scale was developed by a Swedish astronomer named Anders Celsius at the University of Uppsala, Sweden in 1741. This scale was bit different from the scale we know now, though it consisted 0 to 100 degrees, Anders marked the boiling point of water as 0°C, while freezing point of water was 100°C. Upon Celsius' death the points of the scale were reversed to the modern one we now know.

Now what is the connection between Celsius and centigrade you ask? Well, the word centigrade comes from "centi-" meaning 100 and "grade" an abbreviation for gradients. Since the 19th century, the scientific and thermometry communities worldwide started referring to this scale as the centigrade scale, because there were 100 degrees between the defining points (freezing and boiling) of the scale, making it a type of centigrade. The “term” centigrade was introduced in 1744 and remained the primary name for degree of temperature until 1948. In 1948 the CGPM (Conference General des Poids et Measures) decided to standardize the temperature scale.

The term centigrade was phased out as it had another meaning in the Spanish and French language, where it meant a unit of angular measurement, which would make centigrade 1/10,000 of a right angle and also had a similar meaning in other languages. The centigrade was then changed back to the former Celsius scale. The Celsius scale is now most commonly used in Europe and Asia, while Fahrenheit is used in the US and Kelvin is used primarily by the scientific community.

Image Courtesy: lfcstartright.co.uk