In this article, in the context of the character of the relationship between the orthographic norm and the lexical and phonetic levels of the language, the peculiarities of spelling words and morphemes as one of the aspects of the orthographic norm are compared. An attempt is made to ascertain specific characterological features inherent in the orthographic norm of the Middle English and Old Slavonic languages by the material of the XII-century manuscripts corresponding to these languages, by comparing the involved principles of orthography and considering the nature of their relationship with intravariance and extravariance of spelling.