The paper discusses synonymic relations of single root derivatives which are treated ambiguously in linguistics. There are two opposing points of view on this issue: according to one of them derivatives of one nest are considered not to be synonymous, while the other view sees them as derivational synonyms. The status of co-derivatives formed with the help of different affixes with identical meaning is argued most of all. The Buryat action names derived parallel from one verb prove to be synonyms. Special attention here is paid to the causes of deverbatives development. Grouping abstract nouns with the meaning of action-state in derivational sets and defining their structural types illustrate the nature of semantic relations of derivational synonyms, regular nature of their appearance in the language. Word-building nature of verbal bases reflects the derivational potential of verb stems and demonstrates the rich and variable character of the Buryat language. Derivational synonyms develop to denote an object, phenomenon or process referred to more precisely, in turn, synonyms of the same root appear to differ in very subtle (semantic) and stylistic shades.