Aside from this classic example of words that should remain as they are in the original, there are other cases of words that cannot be translated: international symbols.
In this sense, the clearest example is chemical elements. http://en.wikipedia.org/wiki/Chemical_element. For example, if, in our original, “Na” appears, we would not translate it as “Sod.”. Instead, we would leave it as “Na”.
The same happens with measures of length. The abbreviations stay as they are in English and are not translated: http://en.wikipedia.org/wiki/Imperial_units. For example, if in our original, “12 in” appears, we would not translate it as “12 pulg.”. Instead, we would leave it as “12 in.”. What we can do is convert one measurement from one system to another. For example, we can convert feet to meters or vice versa.