Kg or kg: notation Often in many elementary and secondary school books frequented by students aged 6 to 13 years old still write $\mathrm{Kg}$ instead of $\mathrm{kg}$. Many teachers give to the students this notation $\mathrm{Kg}$ that I used when I was a child, i.e. with a capital $\mathrm{Kg}$. Also the newspapers, television, ... use $\mathrm{Kg}$.

To write kilograms with a capital $\mathrm{K}$ is inappropriate or is it possible to use it?

I am disagree with the notation $\mathrm{Kg}$.
 A: It's incorrect, according to the Bureau Internationale des Poids et des Mesures, who are the international authorities on how SI is defined.  Here's their guidance, from the SI Brochure (PDF;  see p. 31 for French or p. 143 for English):

Prefix symbols are printed in upright typeface, as are unit symbols, regardless of the typeface used in the surrounding text and are attached to unit symbols without a space between the prefix symbol and the unit symbol. With the exception of da (deca), h (hecto) and k (kilo), all multiple prefix symbols are upper-case letters and all sub-multiple prefix symbols are lowercase letters. All prefix names are printed in lowercase letters, except at the beginning of a sentence.

A: in nuclear physics we used keV and MeV for gamma ray energy. Usually my student write KeV  or Kev instead of keV which is wrong. My opinion if the symbol capital or small can be understood we can accept it. i.e keV or KeV
because the meaning is known. But in cases like MeV and meV here the meaning is very different one is million electron volt and the other is milli electron volt. So the first can be accepted and the second impossible to be accepted.
