Comment by john-aj

In statistics, one usually differentiates between

- nominal scales (e.g. man/woman),

- ordinal scales (elementary school/middle school/high school),

- interval scales (degrees Celsius) and

- ratio scales (human height, degrees Kelvin).

Only ratio scales may be multiplied and divided. Interval scales may be subtracted and added. Ordinal scales may only be compared (less/greater/equal). Nominal scales may only be compared in terms of (in)equality.

https://en.wikipedia.org/wiki/Level_of_measurement