Whether doublets-synonyms are identical or not?

The article considers pairs of lexical units, which in lexicology are defined as doublets or absolute synonyms. The main idea of the article is to show functional features of doublet units which would allow not to consider such units as absolutely identical. Based on the analysis of Russian nouns, noted in special publications and dictionaries as absolute synonyms, we show that there is often differentiation of elements of lexical pairs. It appears that many absolute synonyms do not disintegrate in the process of their functioning, as linguists predict (due to semantic and formal redundancy of such verbal forms), but many absolute synonyms do exist for a long time without any apparent transformation because there are factors (reasons) in the language that promote their functioning. The analysis shows that a set of factors supporting the existence of doublet forms is specific for the units of terminological character on the one hand, and for generally used absolute synonyms on the other hand.