why is the unit Kelvin (temperature unit) not called "degree Kelvin"? why only "Kelvin"?

thank you for answering.

indeed the unit is kelvin with a lower case k, although the symbol is K.

The degrees scales are so called because the interval chosen was chosen by the inventors of the degF and degC scales, and these two scales have no natural zero. What I mean by the latter is that can't say that 32 degF is half the temperature of 64 degF when comparing across the scales as 32 degF is 0 deg C and 64 deg F is 18 deg C, which is not twice 0! If they were true scales with a natural zero (like km and miles) then you would get the same ratio if you worked in km or miles.

The unit of temperature, Kelvin, is not called "degree Kelvin" because it was decided by the General Conference on Weights and Measures (CGPM) that the word "degree" should not be used for the unit Kelvin. Here's the explanation:

1. The Kelvin scale: The Kelvin scale is an absolute temperature scale, where 0 Kelvin (0 K) represents the lowest possible temperature, known as absolute zero. Unlike other temperature scales like Celsius and Fahrenheit, which have arbitrary zero points, the Kelvin scale is based on absolute quantities of energy.

2. SI unit: The Kelvin is the base unit of temperature in the International System of Units (SI), which is the modern metric system used worldwide. The SI system is designed to be consistent, coherent, and simple. It uses base units without prefixes, except for very large or very small quantities.

3. Name of the unit: The name "Kelvin" was chosen to honor the Scottish physicist William Thomson, 1st Baron Kelvin, who made significant contributions to the field of thermodynamics and proposed the Kelvin temperature scale.

4. No need for "degree": Unlike Celsius and Fahrenheit, the Kelvin scale does not use the term "degree" because it is not based on a fraction or division of a base unit. The SI unit for temperature is simply "Kelvin" without the need for the word "degree."

In summary, the unit of temperature is called "Kelvin" to honor William Thomson, and it does not use the term "degree" because it is an absolute scale without a fractional or arbitrary reference point.