The article offers detailed answers to the questions that are asked in the letters addressed to the Institute of the Russian Language. It discusses three topics: the morphemic structure of the infi nitive and the terminology used to denote the formative affi x; the possibility of forming short roots and the systematical morphological study of theirs, the diffi-culty of morphemic segmentation of the words with short roots; different ways of dividing a word and the connection between syllabus division and methods of teaching reading. The article demonstrates an explanatory approach to the issues of teaching Russian language at school. The fi rst part of the paper explains the choice of the term ‘suffi x’ to denote a formative affi x in the infi nitive. The explanation is based on the description of Russian morphological system, particularly, on the comparison of nominal and verbal word formation. The second part is based on the opposition of names and verbs, the morphemic structure of nominal and verbal word forms. This approach allows us to present the foundations of the internal unity of the Russian morphological system, to show the connection of indivi dual linguistic phenomena with the general laws of the organization of the linguistic system. In the third part, different principles of syllable division and the connection between syllabic division and morphemic division of a wordform are discussed. It is shown that when publishing books for teaching reading, it is necessary to take into account different principles of syllabic division, as well as morphemic division of a word.