The concept of 'translation of realia' is doubly conventional: realia are normally untranslatable (from a dictionary perspective) and, again, are normally not rendered (in context) by means of translation.
With respect to dictionary translation, however, "there are no words that could not be translated into another language, at least descriptively, i.e. by means of a widespread combination of words of the given language", and "what is not possible with respect to a single element, is possible with respect to a complex whole", i.e. with respect to a contextual translation.