Why do we prefix "degree" in temperature measurement scales?

We not only need the name of the reference scale, but to know the measurement units of that scale. There are many redundancies in the English language. Some have been dropped, and others are still around. In any case, we usually drop the name of the reference scale, and just say 85 degrees. The culture is cue enough to know which scale we are using.

So, when the name of the scale is added, it is usually added to the common way of speaking.

Of course, sometimes when asked for the temperature, you just say “95” or “37” without naming the measurement unit nor measurement scale. So sometimes the redundancies do get dropped, and other times not.

Thats..a….really….good…question. The meteorologist is ashamed to not know the answer to this.

…..degree is the ‘unit of measurement’ and Fahrenheit/Celsius/Kelvin are the various scales of the degree unit measured….. sort of USA(Fahrenheit) versus the rest of the world (including all of the scientific world community)

… ‘we ’ DO use degrees Kelvin…...

Oh wait… yes I do. Kelvin is a measure of temperature from absolute zero. Unlike the Celsius or Fahrenheit scales, it is not based on some “arbitrary” zero. For instance, both of those scales are based on the freezing of a liquid (water with or without salt added to the mixture). The Kelvin scale is based on an absolute measurement (absolute zero), so the term “degrees” is not used.

@Les I like the explanation that degree indicates that 0 for that scale is an arbitrary point. That totally makes sense. However, think about the Rankine scale. It starts at absolute zero and yet the degree prefix is used. How do you explain that?

@virtualist I’ve never seen Kelvin used with the degree prefix.

@zaphod beeblebrox: I think, technically, the Rankine is denoted [R], without the degree symbol. The wikipedia article on it says that the degree symbol before [R] is not correct, but I can’t verify that with a better source right now. I think I do remember seeing [R] without the degree symbol in some of my textbooks, which are probably fairly reliable.

@zaphod…... you are dead-on right..

For temperature intervals rather than specific temperatures,
1 K = 1 °C = 1.8 °F = 1.8 °R

@virtualist – But Rankine is based on an absolute (absolute zero). The only difference is that it uses degree F as it’s “base” unit rather than degree C for Kelvin. Technically, it does not use the degree symbol.

Kelvin used to use the degree prefix as well, it was changed in 1967.

Why not use degrees when talking about Kelvins? Well to answer that, we need to make another question… what is a degree anyway?

A degree is a division of a pattern, for example when talking about angles, we measure them in degrees (that is, when we are not using radians), the full circumference of a circle is said to be 360° (degrees), an arbitrary convention that we have been using since the Babylonians, and what they did is that they divide the circle into 360 sections and each of those sections is what we call a degree. So a degree when talking about an angle is ⅓60 of the circumference of a circle. The logic is the same when measuring temperature, and the pattern here is just as relative as the used by the Babylonians.

Since heat changes the state of matter, and temperature tells us how much heated something is, we can make a pattern that can start when there is little heat and ends when there is much heat. But ‘much’ and ‘little’ are too subjective to use for measuring purposes. Lets say that the start of the pattern will be assigned when water freezes and the end will be assigned when water boils. If that pattern is divided into 100 sections, or degrees, assigning 0° when water freezes, and 100° when water boils, and each one of those divisions is what we know as the measuring unit of Celsius degree. It is the same for Fahrenheit degrees, but that same pattern divided in 180 sections or degrees and assigned 32° when water freezes and 212° F when water boils.

There is no pattern like this when talking about Kelvins. It uses that absolute reference of when molecules cease to vibrate, this is when they have no heat(heat makes molecules vibrate), and is stated to be as 0 K (Zero Kelvin, absolute zero, -272°C or -459.67°F), every other temperature takes it from there, those temperatures are a reference to that temperature that is measured when matter is at absolute zero. So there is no pattern when talking about kelvins, therefore there is no need to use degrees (though one Kelvin unit is the same as a one Celsius degree) when talking about Kelvin units.