On several selected samples the paper offers an interpretation of the relationship between typical elements of spoken discourse and the totality of textbook discourse as a written realization of language. The author's main emphasis is on the fact that units of both language levels, (a) the level of functional (grammatical) words and (b) the level of lexical (fully meaning) words, following their specificities, have their essential role in formation of the discourse that would he adjusted to the discourse type that (purposely) is closest to the language of direct communication of the person who interprets the matter of a (school) subject with the person who should accept the given interpretations, i.e. with the personality of a student. The author's conclusion is that it could also he stated for the studied language corpus that the elements of dialogical nature, as an essential characteristic of spoken discourse, are harmoniously integrated with a significant number of narrative elements in textbook definitions.