The article considers fragments of teaching speech culture attracting the language history data. The reason for variation in endings of nouns in the Modern Russian language is seen as a result of interference of the Old Russian language declension types or the influence of the dual number form which was consecutively lost in the language. Students are offered to analyse inflexions of nouns of masculine gender. There is an analysis of variant endings of genitive and prepositional cases in singular, and also the ones of nominative and genitive cases in plural. All these word forms can be equivalent or they can have semantic or stylistic differences.
